Document:

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                                                                   EXHIBIT 10.40

     UNLESS THIS CERTIFICATE IS PRESENTED BY AN AUTHORIZED REPRESENTATIVE OF THE
DEPOSITORY TRUST COMPANY (55 WATER STREET, NEW YORK, NEW YORK) (THE
"DEPOSITARY", WHICH TERM INCLUDES ANY SUCCESSOR DEPOSITARY FOR THE CERTIFICATES)
TO THE ISSUER OR ITS AGENT FOR REGISTRATION OF TRANSFER, EXCHANGE OR PAYMENT,
AND ANY CERTIFICATE ISSUED IS REGISTERED IN THE NAME OF CEDE & CO. OR IN SUCH
OTHER NAME AS REQUESTED BY AN AUTHORIZED REPRESENTATIVE OF THE DEPOSITARY (AND
ANY PAYMENT HEREIN IS MADE TO CEDE & CO. OR TO SUCH OTHER ENTITY AS IS REQUESTED
BY AN AUTHORIZED REPRESENTATIVE OF THE DEPOSITARY), ANY TRANSFER, PLEDGE, OR
OTHER USE HEREOF FOR VALUE OR OTHERWISE BY OR TO ANY PERSON IS WRONGFUL INASMUCH
AS THE REGISTERED OWNER HEREOF, CEDE & CO., HAS AN INTEREST HEREIN.

     THE NOTE EVIDENCED HEREBY HAS NOT BEEN REGISTERED UNDER THE UNITED STATES
SECURITIES ACT OF 1933, AS AMENDED (THE "SECURITIES ACT"), AND ACCORDINGLY MAY
NOT BE OFFERED OR SOLD EXCEPT AS SET FORTH BELOW. BY ITS ACQUISITION HEREOF, THE
HOLDER (1) REPRESENTS THAT IT IS (A) A "QUALIFIED INSTITUTIONAL BUYER" (AS
DEFINED IN RULE 144A UNDER THE SECURITIES ACT), (2) AGREES THAT IT WILL NOT
WITHIN TWO YEARS AFTER THE ORIGINAL ISSUANCE OF THIS NOTE RESELL OR OTHERWISE
TRANSFER THIS NOTE EXCEPT (A) TO iBASIS, INC. OR ANY SUBSIDIARY THEREOF, (B) TO
A QUALIFIED INSTITUTIONAL BUYER IN COMPLIANCE WITH RULE 144A UNDER THE
SECURITIES ACT, OR (C) PURSUANT TO A REGISTRATION STATEMENT WHICH HAS BEEN
DECLARED EFFECTIVE UNDER THE SECURITIES ACT (AND WHICH CONTINUES TO BE EFFECTIVE
AT THE TIME OF SUCH TRANSFER); (3) PRIOR TO SUCH TRANSFER (OTHER THAN A TRANSFER
PURSUANT TO CLAUSE (2)(C) ABOVE), IT WILL FURNISH TO U.S. NATIONAL BANK
ASSOCIATION, AS FISCAL AGENT (OR A SUCCESSOR FISCAL AGENT, AS APPLICABLE), SUCH
CERTIFICATIONS, LEGAL OPINIONS OR OTHER INFORMATION AS THE FISCAL AGENT MAY
REASONABLY REQUIRE TO CONFIRM THAT SUCH TRANSFER IS BEING MADE PURSUANT TO AN
EXEMPTION FROM, OR IN A TRANSACTION NOT SUBJECT TO, THE REGISTRATION
REQUIREMENTS OF THE SECURITIES ACT; AND (4) AGREES THAT IT WILL DELIVER TO EACH
PERSON TO WHOM THIS NOTE IS TRANSFERRED A NOTICE SUBSTANTIALLY TO THE EFFECT OF
THIS LEGEND. IN CONNECTION WITH ANY TRANSFER OF THIS NOTE, THE HOLDER MUST CHECK
THE APPROPRIATE BOX SET FORTH ON THE REVERSE HEREOF RELATING TO THE MANNER OF
SUCH TRANSFER AND SUBMIT THIS CERTIFICATE TO U.S. NATIONAL BANK ASSOCIATION, AS
FISCAL AGENT (OR A SUCCESSOR FISCAL AGENT, AS APPLICABLE). THE FISCAL AGENCY
AGREEMENT CONTAINS A PROVISION REQUIRING THE FISCAL AGENT TO REFUSE TO

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REGISTER ANY TRANSFER OF THIS NOTE IN VIOLATION OF THE FOREGIONG RESTRICTION.

     THE TERMS OF THIS NOTE ARE SUBJECT TO THAT CERTAIN SUBORDINATION AGREEMENT
DATED AS OF JANUARY 30, 2003, AMONG SILICON VALLEY BANK, THE CREDITORS NAMED
THEREIN AND U.S. BANK NATIONAL ASSOCIATION, AS COLLATERAL AGENT AND FISCAL
AGENT.

     THE TERMS OF THIS NOTE ARE FURTHER SUBJECT TO THAT CERTAIN COLLATERAL
AGENCY AND INTERCREDITOR AGREEMENT DATED AS OF FEBRUARY 21, 2003, AMONG THE
SYMPHONY FUNDS NAMED THEREIN, THE EXCHANGING HOLDERS NAMED THEREIN AND U.S. BANK
NATIONAL ASSOCIATION, AS COLLATERAL AGENT, AS THE SAME MAY BE AMENDED, MODIFIED
OR SUPPLEMENTED FROM TIME TO TIME.

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                                  iBASIS, INC.

                               iBASIS GLOBAL, INC.

                       11.5% SENIOR SECURED NOTE DUE 2005

                                                              CUSIP: 450732 AB 8

No.: N-2                                                             $19,075,000

     iBasis, Inc., a corporation duly organized and validly existing under the
laws of the State of Delaware, and iBasis Global, Inc., a corporation duly
organized and validly existing under the laws of the State of Delaware (herein
collectively called the "Issuer", which term includes any successor corporation
under the Fiscal Agency Agreement referred to on the reverse hereof), for value
received hereby, on a joint and several basis, promise to pay to Cede & Co. or
registered assigns, the principal sum of Nineteen Million Seventy-five Thousand
Dollars ($19,075,000) on January 15, 2005, at the office or agency of the Issuer
maintained for that purpose in accordance with the terms of the Fiscal Agency
Agreement, in such coin or currency of the United States of America as at the
time of payment shall be legal tender for the payment of public and private
debts, and to pay interest, semi-annually on January 15 and July 15 of each
year, commencing July 15, 2003, on said principal sum at said office or agency,
in like coin or currency, at the rate per annum of 11.5%, from January 15 or
July 15, as the case may be, next preceding the date of this Note to which
interest has been paid or duly provided for, unless the date hereof is a date to
which interest has been paid or duly provided for, in which case from the date
of this Note, or unless no interest has been paid or duly provided for on the
Notes, in which case from January 30, 2003 (regardless of whether such date
occurs prior to the date on which this Note is issued), until payment of said
principal sum has been made or duly provided for. Notwithstanding the foregoing,
if the date hereof is after any January 1 or July 1, as the case may be, and
before the following January 15 or July 15, this Note shall bear interest from
such January 15 or July 15; provided, however, that if the Issuer shall default
in the payment of interest due on such January 15 or July 15, then this Note
shall bear interest from the next preceding January 15 or July 15 to which
interest has been paid or duly provided for or, if no interest has been paid or
duly provided for on such Note, from January 30, 2003 (regardless of whether
such date occurs prior to the date on which this Note is issued). Except as
otherwise provided in the Fiscal Agency Agreement or the Exchange Agreement
referred to on the reverse hereof, the interest payable on the Note pursuant to
the Exchange Agreement on any January 15 or July 15 will be paid to the Person
entitled thereto as it appears in the Note register at the close of business on
the record date, which shall be the January 1 or July 1 (whether or not a
Business Day) next preceding such January 15 or July 15, as provided in the
Fiscal Agency Agreement; provided, however, that any such interest not
punctually paid or duly provided for shall be payable as provided in the
Exchange Agreement or the Fiscal Agency Agreement. Interest may, at the option
of the Issuer, be paid either (i) by check mailed to the registered address of
such Person (provided that the holder of Notes with an aggregate principal
amount in excess of $2,000,000 shall, at the written election of such holder, be
paid by wire transfer of immediately available funds) or (ii) by transfer to an
account maintained by such Person located in the United States; provided,
however, that payments to the Depositary will

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be made by wire transfer of immediately available funds to the account of the
Depositary or its nominee.

     Reference is made to the further provisions of this Note set forth on the
reverse hereof, including, without limitation, provisions subordinating the
payment of principal of and premium, if any, and interest on the Notes to the
prior payment in full of all Senior Debt, as defined in the Subordination
Agreement referred to on the reverse hereof. Such further provisions shall for
all purposes have the same effect as though fully set forth at this place.

     This Note shall be deemed to be a contract made under the laws of The
Commonwealth of Massachusetts, and for all purposes shall be construed in
accordance with and governed by the laws of The Commonwealth of Massachusetts,
without regard to the principles of conflicts of laws.

     This Note shall not be valid or become obligatory for any purpose until the
certificate of authentication hereon shall have been manually signed by the
Fiscal Agent or a duly authorized authenticating agent under the Fiscal Agency
Agreement.

<Page>

     IN WITNESS WHEREOF, the Issuer has caused this Note to be duly executed.

                                        iBASIS, INC.

                                        By:       /s/ Ofer Gneezy
                                            ------------------------------------
                                            Name:  Ofer Gneezy
                                                   -----------------------------
                                            Title: President & CEO
                                                   -----------------------------

                                        iBASIS GLOBAL, INC.

                                        By:       /s/ Richard Tennant
                                            ------------------------------------
                                            Name:  Richard Tennant
                                                   -----------------------------
                                            Title: Treasurer and CFO
                                                   -----------------------------

Dated: February 21, 2003

FISCAL AGENT'S CERTIFICATE OF AUTHENTICATION

This is one of the Notes described in the within-named Fiscal Agency Agreement.

U.S. BANK NATIONAL ASSOCIATION, as Fiscal Agent

By:        /s/ John Brennan
    ------------------------------------
    Name:  John A. Brennan
    Title: Trust Officer

By:
    ------------------------------------
          As Authenticating Agent
     (if different from Fiscal Agent)

<Page>

                                 REVERSE OF NOTE

                                  iBASIS, INC.

                               iBASIS GLOBAL, INC.

                       11.5% SENIOR SECURED NOTES DUE 2005

     This Note is one of a duly authorized issue of Notes of the Issuer,
designated as its 11.5% Senior Secured Notes Due 2005 (herein called the
"Notes"), limited to the aggregate principal amount of $19,075,000, all issued
or to be issued under and pursuant to (x) a Securities Exchange Agreement dated
as of January 30, 2003 (herein called the "Symphony Exchange Agreement"), among
the Issuer, iBasis Securities Corporation, the Symphony Funds party thereto and
U.S. Bank National Association, as collateral agent (herein called the
"Collateral Agent"), and (y) a Securities Exchange Agreement dated as of
February 21, 2003 (herein called the "Permitted Exchange Agreement" and,
together with the Symphony Exchange Agreement, the "Exchange Agreements"), among
the Issuer, iBasis Securities Corporation, the Exchanging Holders party thereto
and the Collateral Agent, to which Exchange Agreements and all exchange
agreements supplemental thereto reference is hereby made for a description of
the rights, limitations of rights, obligations, duties and immunities thereunder
of the Collateral Agent, the Issuer and the holders of the Notes. The Issuer has
appointed U.S. Bank National Association as fiscal agent, (herein called the
"Fiscal Agent") and as paying agent in respect of the Notes upon the terms and
subject to the conditions contained in a Fiscal Agency Agreement dated as of
January 30, 2003, as amended by Amendment No. 1 to Fiscal Agency Agreement dated
as of February 21, 2003 (as amended, the "Fiscal Agency Agreement"), between the
Issuer and the Fiscal Agent.

     In case an Event of Default (as defined in the Exchange Agreements) shall
have occurred and be continuing, the principal of, premium, if any, and accrued
interest on all Notes may be declared by either the Collateral Agent or the
holders of not less than 25% in aggregate principal amount of the Notes then
outstanding, and upon said declaration shall become, due and payable, in the
manner, with the effect and subject to the conditions provided in the Exchange
Agreements.

     The Exchange Agreements contain provisions prohibiting the changing,
waiver, discharge or termination of the Exchange Agreements without the consent
of each holder of a Note directly affected thereby if such change, waiver,
discharge or termination shall (i) extend the fixed maturity of any Note, or
reduce the rate or extend the time of payment of interest thereon, or reduce the
principal amount thereof, (ii) amend, modify or waive the provisions of Section
13.4 of either Exchange Agreement, (iii) reduce the percentage specified in, or
otherwise modify the definition of "Demand Holders" or "Required Holders" stated
therein, (iv) consent to the assignment or transfer by the Issuer of any of its
rights and obligations under the Exchange Agreements, (v) establish any new
obligations for any holder of a Note not relating to the subject matter of the
Exchange Agreements or (ii) release all or substantially all of the collateral
or guarantees with respect to the Obligations specified in the Exchange
Agreements. Subject to the provisions of the Exchange Agreements, the holders of
a majority in aggregate principal amount of the Notes at the time

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outstanding may on behalf of the holders of all of the Notes waive any past
Default or Event of Default under the Exchange Agreements and its consequences
except a default in the payment of interest. Any such consent or waiver by the
holder of this Note (unless revoked as provided in the Exchange Agreements)
shall be conclusive and binding upon such holder and upon all future holders and
owners of this Note and any Notes which may be issued in exchange or
substitution hereof, irrespective of whether or not any notation thereof is made
upon this Note or such other Notes.

     The indebtedness evidenced by the Notes is, to the extent and in the manner
provided in the Subordination Agreement dated as of January 30, 2003 (herein
called the "Subordination Agreement"), among the Investors party thereto,
Silicon Valley Bank, and U.S. Bank National Association, subordinated and
subject in right of payment to the prior payment in full of all Senior Debt (as
defined in the Subordination Agreement), and this Note is issued subject to the
provisions of the Subordination Agreement with respect to such subordination.
Each holder of this Note, by accepting the same, agrees to and shall be bound by
such provisions.

     No reference herein to the Exchange Agreements, the Fiscal Agency Agreement
or the Subordination Agreement and no provision of this Note or of the Exchange
Agreements, the Fiscal Agency Agreement or the Subordination Agreement shall
alter or impair the obligation of the Issuer, which is absolute and
unconditional, to pay the principal of and any premium and interest on this Note
at the place, at the respective times, at the rate and in the coin or currency
herein prescribed.

     Interest on the Notes shall be computed on the basis of a 360-day year of
twelve 30-day months.

     The Notes are issuable in registered form, without coupons, in
denominations of $1,000 principal amount and any integral multiple of $1,000. At
the office or agency of the Issuer referred to on the face hereof, and in the
manner and subject to the limitations provided in the Exchange Agreements,
without payment of any service charge but with payment of a sum sufficient to
cover any tax, assessment or other governmental charge that may be imposed in
connection with any registration or exchange of Notes, Notes may be exchanged
for a like aggregate principal amount of Notes of any other authorized
denominations.

     The Notes may be prepaid at the election of the Issuer, as a whole or in
part from time to time, at any time, upon notice as set forth in Section 4.2 of
the Exchange Agreements, at the following prepayment prices (expressed in
percentages of the outstanding principal amount of the Note, as the case may be,
being prepaid) plus accrued and unpaid interest on such prepaid principal amount
to the prepayment date, MINUS the number of percentage points reflected by the
product of (i) 10.1695 and (ii) the difference between (A) the average closing
trading price of the Common Stock of iBasis, Inc. (the "Common Stock") for the
five trading days immediately prior to, but not including, the date of such
prepayment and (B) the Common Stock price denoted below in the column titled
"Minimum Common Stock Price" (the "Note Prepayment Price"); provided, however,
that in no event shall the Note Prepayment Price be less than 100% of the
outstanding principal amount of the Notes to be prepaid, plus accrued and unpaid
interest on such principal amount to the prepayment date:

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<Table>
<Caption>
                                              PERCENTAGE OF
                                              OUTSTANDING PRINCIPAL   MINIMUM COMMON
DATE OF PREPAYMENT                            AMOUNT                  STOCK PRICE
------------------                            ---------------------   --------------

     After           Prior To and Including
     -----           ----------------------
<S>                       <C>                              <C>               <C>
January 15, 2003          July 15, 2003                    123.0000%         $ 2.25

July 15, 2003             January 15, 2004                 117.2500%         $ 3.50

January 15, 2004          July 15, 2004                    111.5000%         $ 4.25

July 15, 2004             January 15, 2005                 105.7500%         $ 5.00
</Table>

     If a Change of Control (as defined in the Exchange Agreements) occurs at
any time prior to maturity of the Notes, the Issuer shall, within one Business
Day, make an offer to prepay all of the Notes then outstanding at the Note
Prepayment Price set forth above. If the Issuer or any Subsidiary receives any
Net Asset Sale Proceeds (as defined in the Exchange Agreements) in excess of
$250,000 (or if a Default or an Event of Default shall then exist, regardless of
amount), which in each such case does not result in a Change of Control, then
the Issuer shall, within one Business Day pay (or cause its Subsidiary receiving
such proceeds to pay) to the holders as a prepayment of the Notes the lesser of
(a) the amount of such Net Asset Sale Proceeds and (b) the Aggregate Prepayment
Amount (excluding any portion of such Net Asset Sale Proceeds which so long as
no Default or Event of Default exists, (x) in the case of proceeds of business
interruption insurance, is used in the ordinary course of the Issuer's and its
Subsidiaries' business and (y) in the case of proceeds of casualty insurance, is
applied for the purpose of replacing, repairing, restoring or rebuilding the
relevant tangible property).

     Upon due presentment for registration of transfer of this Note at the
office or agency of the Issuer maintained for that purpose in accordance with
the terms of the Fiscal Agency Agreement, a new Note or Notes of authorized
denominations for an equal aggregate principal amount will be issued to the
transferee in exchange thereof; subject to the limitations provided in the
Exchange Agreements and the Fiscal Agency Agreement, without charge except for
any tax, assessment or other governmental charge imposed in connection
therewith.

     The Issuer, the Fiscal Agent, any authenticating agent, any paying agent
and any Note registrar may deem and treat the registered holder hereof as the
absolute owner of this Note (whether or not this Note shall be overdue and
notwithstanding any notation of ownership or other writing hereon made by anyone
other than the Issuer or any Note registrar) for the purpose of receiving

<Page>

payment hereof, or on account hereof, for the conversion hereof and for all
other purposes, and neither the Issuer nor the Fiscal Agent nor any other
authenticating agent nor any paying agent nor other conversion agent nor any
Note registrar shall be affected by any notice to the contrary. All payments
made to or upon the order of such registered holder shall, to the extent of the
sum or sums paid, satisfy and discharge liability for monies payable on this
Note.

     No recourse for the payment of the principal of or any premium or interest
on this Note, or for any claim based hereon or otherwise in respect hereof, and
no recourse under or upon any obligation, covenant or agreement of the Issuer in
the Exchange Agreements or any supplemental exchange agreement or in any Note,
or because of the creation of any indebtedness represented thereby, shall be had
against any incorporator, stockholder, employee, agent, officer or director or
subsidiary, as such, past, present or future, of the Issuer or of any successor
corporation, either directly or through the Issuer or any successor corporation,
whether by virtue of any constitution, statute or rule of law or by the
enforcement of any assessment or penalty or otherwise, all such liability being,
by acceptance hereof and as part of the consideration for the issue hereof,
expressly waived and released.

     This Note shall be deemed to be a contract made under the laws of The
Commonwealth of Massachusetts, and for all purposes shall be construed in
accordance with the laws of The Commonwealth of Massachusetts, without regard to
principles of conflicts of laws.

     Terms used in this Note and defined in the Exchange Agreements are used
herein as therein defined.

<Page>

                                  ABBREVIATIONS

     The following abbreviations, when used in the inscription of the face of
this Note, shall be construed as though they were written out in full according
to applicable laws or regulations.

     TEN COM - as tenants in common

     TEN ENT - as tenant by the entireties

     JT TEN - as joint tenants with right of survivorship and not as tenants in
     common

     UNIF GIFT MIN ACT - ____________ Custodian _____________
                            (Cust)                 (Minor)

     under Uniform Gifts to Minors Act

     --------------------------------------------
                       (State)

     Additional abbreviations may also be used though not in the above list.

<Page>

                                   ASSIGNMENT

     FOR VALUE RECEIVED the undersigned hereby sell(s), assign(s) and
transfer(s) unto

---------------------------------------------------------------

---------------------------------------------------------------

PLEASE INSERT SOCIAL SECURITY OR
OTHER IDENTIFYING NUMBER OF ASSIGNEE

--------------------------------------------------------------------------------

---------------------------------------------------------------

---------------------------------------------------------------
           (Please print or typewrite name and address
               including postal zip code of assignee)

---------------------------------------------------------------

the within Note and all rights thereunder, and hereby irrevocably constitutes
and appoints

---------------------------------------------------------------

Attorney to transfer said Note on the books of the Issuer, with full power of
substitution in the premises.

     In connection with any transfer of the Note (other than any transfer
pursuant to a registration statement that has been declared effective under the
Securities Act), the undersigned confirms that such Note is being transferred:

<Page>

     / /  To iBasis, Inc. or a subsidiary thereof; or

     / /  Pursuant to and in compliance with Rule 144A under the Securities Act
          of 1933, as amended;

and unless the box below is checked, the undersigned confirms that such Note is
not being transferred to an "affiliate" of the Issuer as defined in Rule 144
under the Securities Act of 1933, as amended (an "Affiliate").

     / /  The transferee is an Affiliate of the Issuer.

Dated:____________

                                              ----------------------------------

                                              ----------------------------------
                                              Signature(s)

                                              Signature(s) must be guaranteed by
                                              an "eligible guarantor
                                              institution" meeting the
                                              requirements of the Note
                                              registrar, which requirements
                                              include membership or
                                              participation in the Security
                                              Transfer Agent Medallion Program
                                              ("STAMP") or such other "signature
                                              guarantee program" as may be
                                              determined by the Note registrar
                                              in addition to, or in substitution
                                              for, STAMP, all in accordance with
                                              the Securities Exchange Act of
                                              1934, as amended.

                                              ----------------------------------
                                              Signature Guarantee

NOTICE: The signature of the assignment must correspond with the name as written
upon the face of the Note in every particular without alteration or enlargement
or any change whatever.<Page>

                                                                   Exhibit 10.41

     THIS SECURITY IS A GLOBAL SECURITY WITHIN THE MEANING OF THE AMENDED AND
RESTATED WARRANT AND REGISTRATION RIGHTS AGREEMENT HEREINAFTER REFERRED TO AND
IS REGISTERED IN THE NAME OF A DEPOSITORY OR A NOMINEE OF A DEPOSITORY OR A
SUCCESSOR DEPOSITORY. THIS SECURITY IS NOT EXCHANGABLE FOR SECURITIES REGISTERED
IN THE NAME OF A PERSON OTHER THAN THE DEPOSITORY OR ITS NOMINEE EXCEPT IN THE
LIMITED CIRCUMSTANCES DESCRIBED IN THE AMENDED AND RESTATED WARRANT AND
REGISTRATION RIGHTS AGREEMENT, AND NO TRANSFER OF THIS SECURITY (OTHER THAN A
TRANSFER OF THIS SECURITY AS A WHOLE BY THE DEPOSITORY TO A NOMINEE OF THE
DEPOSITORY OR BY A NOMINEE OF THE DEPOSITORY TO THE DEPOSITORY OR ANOTHER
NOMINEE OF THE DEPOSITORY) MAY BE REGISTERED EXCEPT IN THE LIMITED CIRCUMSTANCES
DESCRIBED IN THE AMENDED AND RESTATED WARRANT AND REGISTRATION RIGHTS AGREEMENT.
UNLESS THIS CERTIFICATE IS PRESENTED BY AN AUTHORIZED REPRESENTATIVE OF THE
DEPOSITORY TRUST COMPANY, A NEW YORK CORPORATION ("DTC"), TO THE ISSUER OR ITS
AGENT FOR REGISTRATION OF TRANSFER, EXCHANGE, OR PAYMENT, AND ANY CERTIFICATE
ISSUED IS REGISTERED IN THE NAME OF CEDE & CO. OR IN SUCH OTHER NAME AS IS
REQUESTED BY AN AUTHORIZED REPRESENTATIVE OF DTC (AND ANY PAYMENT IS MADE TO
CEDE & CO. OR TO SUCH OTHER ENTITY AS IS REQUESTED BY AN AUTHORIZED
REPRESENTATIVE OF DTC), ANY TRANSFER, PLEDGE OR OTHER USE HEREOF FOR VALUE OR
OTHERWISE BY OR TO ANY PERSON IS WRONGFUL INASMUCH AS THE REGISTERED OWNER
HEREOF, CEDE & CO., HAS AN INTEREST HEREIN.

     THIS SECURITY HAS NOT BEEN REGISTERED UNDER THE UNITED STATES SECURITIES
ACT OF 1933, AS AMENDED (THE "SECURITIES ACT"), AND, ACCORDINGLY, MAY NOT BE
OFFERED OR SOLD EXCEPT AS SET FORTH BELOW. BY ITS ACQUISITION HEREOF, THE HOLDER
(1) REPRESENTS THAT IT IS A "QUALIFIED INSTITUTIONAL BUYER" (AS DEFINED IN RULE
144A UNDER THE SECURITIES ACT), (2) AGREES THAT IT WILL NOT WITHIN TWO YEARS
AFTER THE ORIGINAL ISSUANCE OF THIS SECURITY RESELL OR OTHERWISE TRANSFER THIS
SECURITY EXCEPT (A) TO THE ISSUER OR ANY SUBSIDIARY THEREOF, (B) TO A QUALIFED
INSTITUTIONAL BUYER IN COMPLIANCE WITH RULE 144A UNDER THE SECURITIES ACT, OR
(C) PURSUANT TO A REGISTRATION STATEMENT WHICH HAS BEEN DECLARED EFFECTIVE UNDER
THE SECURITIES ACT (AND WHICH CONTINUES TO BE EFFECTIVE AT THE TIME OF SUCH
TRANSFER) AND (3) AGREES THAT IT WILL DELIVER TO EACH PERSON TO WHOM THIS
SECURITY IS TRANSFERRED A NOTICE SUBSTANTIALLY TO THE EFFECT OF THIS LEGEND.

     THE SHARES OF STOCK PURCHASABLE UPON EXERCISE OF THE WARRANTS REPRESENTED
BY THIS CERTIFICATE ARE ALSO SUBJECT TO THE AMENDED AND RESTATED WARRANT AND
REGISTRATION RIGHTS AGREEMENT

<Page>

TO WHICH THE ISSUER AND THE WARRANT AGENT ARE PARTY, A COPY OF WHICH MAY BE
INSPECTED AT THE PRINCIPAL OFFICE OF THE ISSUER OR OBTAINED FROM THE ISSUER
WITHOUT CHARGE.

                                       -2-
<Page>

                                  iBASIS, INC.

No. W-2                                                       3,798,811 Warrants

CUSIP NO: 450732 11 0

                               WARRANT CERTIFICATE

     This Warrant Certificate certifies that CEDE & Co., or its registered
assigns, is the registered holder of warrants expiring January 15, 2008 (the
"Warrants") to purchase shares of Common Stock, par value $0.001 per share (the
"Common Stock"), of iBasis, Inc., a Delaware Corporation (the "Company"). Each
Warrant entitles the holder upon exercise to receive from the Company on or
after the date of issuance of such Warrant and on or before 5:00 P.M. Boston
Time on January 15, 2008 (the "Expiration Date"), one fully paid and
nonassessable share of Common Stock (a "Warrant Share") at the initial exercise
price (the "Exercise Price") of $0.65 payable in lawful money of the United
States of America upon surrender of this Warrant Certificate and payment of the
Exercise Price at the office or agency of the Warrant Agent, but only subject to
the conditions set forth herein and in the Amended and Restated Warrant and
Registration Rights Agreement referred to on the reverse hereof. The Exercise
Price and number of Warrant Shares issuable upon exercise of the Warrants are
subject to adjustment upon the occurrence of certain events set forth in the
Amended and Restated Warrant and Registration Rights Agreement.

     No Warrant may be exercised after the Expiration Date, and to the extent
not exercised by such time such warrants shall become void.

     This Warrant Certificate shall not be valid unless countersigned by the
Warrant Agent, as such term is used in the Amended and Restated Warrant and
Registration Rights Agreement.

     This Warrant Certificate, and all actions, claims and conduct relating
thereto, shall be governed by and construed in accordance with the laws of The
Commonwealth of Massachusetts, without regard to the principles of conflicts of
laws.

                                       -3-
<Page>

     IN WITNESS WHEREOF, iBasis, Inc., has caused this Warrant Certificate to be
duly executed.

Dated:  February 21, 2003

                                          iBASIS, INC.

                                          By:    /s/ Ofer Gneezy
                                             -----------------------------------
                                                 Name:  Ofer Gneezy
                                                 Title: President & CEO

WARRANT AGENT'S CERTIFICATE OF AUTHENTICATION
This is one of the Warrants described in the within-named Amended and Restated
Warrant and Registration Rights Agreement.

U.S. BANK NATIONAL ASSOCIATION, as Warrant Agent

By:      /s/ John A. Brennan
    -----------------------------------
    Name:    John A. Brennan
    Title:   Trust Officer

By:
    -----------------------------------
         As Authenticating Agent
     (if different from Warrant Agent)

<Page>

                                  iBASIS, INC.

     The Warrants evidenced by this Warrant Certificate are part of a duly
authorized issue of Warrants expiring January 15, 2008, entitling the holder on
exercise to receive shares of Common Stock and are issued or to be issued
pursuant to the Amended and Restated Warrant and Registration Rights Agreement
dated as of February 21, 2003 (the "Amended and Restated Warrant and
Registration Rights Agreement"), duly executed and delivered by the Company to
U.S. Bank National Association, as warrant agent (the "Warrant Agent"), which
Amended and Restated Warrant and Registration Rights Agreement is hereby
incorporated by reference in and made a part of this instrument and is hereby
referred to for a description of the rights, limitation of rights, obligations,
duties and immunities thereunder of the Warrant Agent, the Company and the
holders (the words "holders" or "holder" meaning the registered holders or
registered holder) of the Warrants. A copy of this Amended and Restated Warrant
and Registration Rights Agreement may be obtained by the holder hereof upon
written request to the Company. Capitalized terms used herein without being
otherwise defined shall have the meaning ascribed to them in the Amended and
Restated Warrant and Registration Rights Agreement.

     Each Warrant may be exercised at any time on or after the date of issuance
of such Warrant and on or before the Expiration Date. The holder of Warrants
evidenced by this Warrant Certificate may exercise them as follows:

               (I)   The Warrants evidenced by this Warrant Certificate may be
          exercised by the holder hereof, in whole or in part, during normal
          business hours on any Business Day on or prior to the Expiration Date,
          by surrender of this Warrant Certificate to the Company at its
          principal office, accompanied by a subscription substantially in the
          form attached to this Warrant Certificate duly executed by such holder
          and accompanied by (a) wire transfer of immediately available funds or
          (b) certified or official bank check payable to the order of the
          Company, in each case in the amount obtained by multiplying (i) the
          number of shares of Common Stock (without giving effect to any
          adjustment thereof pursuant to the provisions of the Amended and
          Restated Warrant and Registration Rights Agreement) for which the
          Warrant evidenced by this Warrant Certificate is then being exercised,
          as designated in such subscription, by (ii) the Initial Exercise
          Price. Thereupon, such holder shall be entitled to receive the number
          of duly authorized, validly issued, fully paid and nonassessable
          shares of Common Stock (or Other Securities) determined as provided in
          Sections 6 and 7 of the Amended and Restated Warrant and Registration
          Rights Agreement.

               (II)  The Warrants evidenced by this Warrant Certificate may be
          converted by the holder hereof, in whole or in part, into shares of
          Common Stock (or Other Securities), during normal business hours on
          any Business Day on or prior to the Expiration Date, by surrender of
          this Warrant Certificate to the Company at its principal office,
          accompanied by a conversion notice substantially in the form attached
          to this Warrant Certificate duly executed by such holder. Thereupon,
          such holder shall be entitled to receive a number of duly authorized,
          validly issued, fully paid and nonassessable shares of Common Stock
          (or Other Securities) equal to:

          (a)  the excess of

<Page>

               (i) (x) the number of shares of Common Stock (or Other
          Securities) determined as provided in Sections 6 and 7 of the Amended
          and Restated Warrant and Registration Rights Agreement which such
          holder would be entitled to receive upon exercise of the Warrants
          represented by this Warrant Certificate for the number of shares of
          Common Stock designated in such conversion notice (without giving
          effect to any adjustment thereof pursuant to Sections 6 or 7 of the
          Amended and Restated Warrant and Registration Rights Agreement)
          MULTIPLIED BY (y) the Current Market Price of each such share of
          Common Stock (or such Other Securities) so receivable upon such
          exercise

          OVER

               (ii) (x) the number of shares of Common Stock (without giving
          effect to any adjustment thereof pursuant to Sections 6 or 7 of the
          Amended and Restated Warrant and Registration Rights Agreement or
          other provisions thereof) which such holder would be entitled to
          receive upon exercise of the Warrants represented by this Warrant
          Certificate for the number of shares of Common Stock designated in
          such conversion notice (without giving effect to any adjustment
          thereof pursuant to Sections 6 or 7 of the Amended and Restated
          Warrant and Registration Rights Agreement) MULTIPLIED BY (y) the
          Initial Exercise Price

          DIVIDED BY

          (b) such Current Market Price of each such share of Common Stock (or
          Other Securities).

               (III) The Warrant represented by this Warrant Certificate may be
          exercised by the holder hereof, in whole or in part, during normal
          business hours on any Business Day on or prior to the Expiration Date,
          by surrender of this Warrant Certificate to the Company at its
          principal office, accompanied by a note tender notice substantially in
          the form attached to this Warrant Certificate duly executed by such
          holder and accompanied by a Note. Thereupon, such holder shall be
          deemed to have exercised the Warrant represented by this Warrant
          Certificate for the number of shares of Common Stock (up to the
          maximum number of shares of Common Stock set forth on the face of this
          Warrant Certificate and without giving effect to any adjustment
          thereof pursuant to Sections 6 or 7 of the Amended and Restated
          Warrant and Registration Rights Agreement or other provisions thereof)
          obtained by dividing (i) the sum of the outstanding face amount of
          such Note (or such lesser amount indicated on the note tender notice)
          PLUS any cash or payment-in-kind interest accrued on such Note, PLUS
          any accrued prepayment penalty or premium by (ii) the Exercise Price.
          Thereupon, such holder shall be entitled to receive the number of duly
          authorized, validly issued, fully paid and nonassessable shares of
          Common Stock (or Other Securities) determined as provided in Sections
          6 and 7 of the Amended and Restated Warrant and Registration Rights
          Agreement.

          In the event that upon any exercise of Warrants evidenced hereby the
number of Warrants exercised shall be less than the total number of Warrants
evidenced hereby, there shall be issued to the holder hereof or its assignee a
new Warrant Certificate of like tenor, dated the date hereof and calling in the
aggregate on the face or faces thereof for the number of Warrants (without
giving effect to any adjustment thereof pursuant to the terms of the Amended and

                                       -6-
<Page>

Restated Warrant and Registration Rights Agreement) to the number of Warrants
called for on the face of this Warrant Certificate minus the number of Warrants
designated by the holder upon such exercise.

     Upon the exercise of the Warrants evidenced by this Warrant Certificate as
provided above, the Company may elect either (i) to comply with the requirements
of Section 7.3(a) of the Amended and Restated Warrant and Registration Rights
Agreement with respect to the issuance of shares of Common Stock in connection
with such exercise or (ii) upon written notice to the holder not more than two
Business Days following the date of exercise, to pay to the holder an amount
equal to the Market Price for each share of Common Stock issuable upon such
exercise (the "Cash Close Out") in lieu of issuing such Common Stock. Any Cash
Close Out made in accordance with this paragraph shall be paid within two
Business Days of the exercise of the Warrants evidenced by this Warrant
Certificate by (a) wire transfer of immediately available funds or (b) certified
or official bank check payable to the order of the holder hereof.

     The Company will not be required to issue fractional shares of Common Stock
upon exercise of the Warrants or distribute share certificates that evidence
fractional shares of Common Stock. In lieu of fractional shares of Common Stock,
there may be paid to the registered Holder of this Warrant Certificate at the
time such Warrant Certificate is exercised an amount in cash equal to the same
fraction of the Current Market Value per share of Common Stock on the Business
Day immediately proceeding the date this Warrant Certificate is surrendered for
exercise.

     The holders of the Warrants are entitled to certain registration rights
with respect to the Common Stock purchasable upon exercise thereof. Such
registration rights are set forth in Section 8 of the Amended and Restated
Warrant and Registration Rights Agreement.

     Warrant Certificates, when surrendered at the office of the Warrant Agent
by the registered holder thereof in person or by legal representative or
attorney duly authorized in writing, may be exchanged, in the manner and subject
to the limitations provided in the Amended and Restated Warrant and Registration
Rights Agreement, but without payment of any service charge, for another Warrant
Certificate or Warrant Certificates of like tenor evidencing in the aggregate a
like number of Warrants.

     Upon due presentation for registration of transfer of this Warrant
Certificate at the office of the Warrant Agent a new Warrant Certificate or
Warrant Certificates of like tenor and evidencing in the aggregate a like number
of Warrants shall be issued to the transferee(s) in exchange for this Warrant
Certificate, subject to the limitations provided in the Amended and Restated
Warrant and Registration Rights Agreement, without charge except for any tax or
other governmental charge imposed in connection therewith.

     The Company and the Warrant Agent may deem and treat the registered
holder(s) thereof as the absolute owner(s) of this Warrant Certificate
(notwithstanding any notation of ownership or other writing hereon made by
anyone), for the purpose of any exercise hereof, of any distribution to the
holder(s) hereof, and for all other purposes, and neither the Company nor the
Warrant Agent shall be affected by any notice to the contrary. Neither the
Warrants nor this Warrant Certificate entitled any holder hereof to any rights
of a stockholder of the Company.

                                       -7-
<Page>

                              FORM OF SUBSCRIPTION

                 [To be executed only upon exercise of Warrant]

To iBasis, Inc.:

     The undersigned hereby irrevocably elects to exercise the right,
represented by this Warrant Certificate, to receive __________(1) shares of the
Common Stock and herewith makes payment of $_____ in accordance with the terms
hereof, and requests that the certificates for such shares be issued in the name
of, and delivered to _______________, whose address is as follows:

Dated:
                                              ----------------------------------
                                              (Signature must conform in all
                                              respects to name of holder as
                                              specified on the face of Warrant)

                                              ----------------------------------
                                              (Street Address)

                                              ----------------------------------
                                              (City)     (State)      (Zip Code)

----------
(1) Insert here the number of shares called for on the face of this Warrant
Certificate (or, in the case of a partial exercise, the portion thereof as to
which the Warrant evidenced by this Warrant Certificate is being exercised), in
either case without making any adjustment for any stock or other securities or
property or cash which, pursuant to the adjustment provisions of the Warrant
evidenced by this Warrant Certificate, may be delivered upon exercise. In the
case of a partial exercise, a new Warrant Certificate will be issued and
delivered, representing the unexercised portion of the Warrant evidenced by this
Warrant Certificate, to the holder surrendering the Warrant Certificate.

                                       -8-
<Page>

                               FORM OF ASSIGNMENT

                 [To be executed only upon transfer of Warrant]

     For value received, the undersigned registered holder of the Warrants
evidenced by this Warrant Certificate hereby sells, assigns and transfers unto
__________________the right represented by such Warrant Certificate to purchase
_______(2) shares of Common Stock of iBasis, Inc. to which such Warrant
Certificate relates, and appoints _______________Attorney to make such transfer
on the books of iBasis, Inc. maintained for such purpose, with full power of
substitution in the premises.

Dated:
                                              ----------------------------------
                                              (Signature must conform in all
                                              respects to name of holder as
                                              specified on the face of Warrant)

                                              ----------------------------------
                                              (Street Address)

                                              ----------------------------------
                                              (City)     (State)      (Zip Code)

Signed in the presence of:

----------
(2) Insert here the number of shares called for on the face of this Warrant
Certificate (or, in the case of a partial transfer, the portion thereof as to
which the Warrant evidenced by this Warrant Certificate is being transferred),
in either case without making any adjustment for any stock or other securities
or property or cash which, pursuant to the adjustment provisions of the Warrant
evidenced by this Warrant Certificate, may be delivered upon exercise. In the
case of a partial transfer, a new Warrant Certificate will be issued and
delivered, representing the non-transferred portion of the Warrants evidenced by
this Warrant Certificate, to the holder transferring the Warrants.

                                       -9-
<Page>

                            FORM OF CONVERSION NOTICE

To iBasis, Inc.:

     The undersigned registered holder of the Warrants evidenced by this Warrant
Certificate hereby irrevocably converts such Warrants with respect to _______(3)
shares of the Common Stock which such holder would be entitled to receive upon
the exercise hereof, and requests that the certificates for such shares be
issued in the name of, and delivered to _________________, whose address is as
follows:

Dated:
                                              ----------------------------------
                                              (Signature must conform in all
                                              respects to name of holder as
                                              specified on the face of Warrant)

                                              ----------------------------------
                                              (Street Address)

                                              ----------------------------------
                                              (City)     (State)      (Zip Code)

----------
(3) Insert here the number of shares called for on the face of this Warrant
Certificate (or, in the case of a partial conversion, the portion thereof as to
which the Warrants evidenced by this Warrant Certificate are being converted),
in either case without making any adjustment for additional shares of Common
Stock or any other stock or other securities or property or cash which, pursuant
to the adjustment provisions of the Warrant evidenced by this Warrant
Certificate, may be delivered upon exercise. In the case of a partial
conversion, a new Warrant Certificate will be issued and delivered, representing
the unconverted portion of the Warrants, to the holder surrendering this Warrant
Certificate.

                                      -10-
<Page>

                               FORM OF NOTE TENDER

          [To be executed only upon a note tender exercise of Warrant]

To iBasis, Inc.:

     The undersigned registered holder of the Warrants evidenced by this Warrant
Certificate hereby irrevocably exercises such Warrants for, and purchases
thereunder, __________(4) shares of the Common Stock and herewith makes payment
of $_____ therefore by virtue of tendering the attached Note, and requests that
the certificates for such shares be issued in the name of, and delivered to
_______________, whose address is as follows:

Dated:
                                              ----------------------------------
                                              (Signature must conform in all
                                              respects to name of holder as
                                              specified on the face of Warrant)

                                              ----------------------------------
                                              (Street Address)

                                              ----------------------------------
                                              (City)     (State)      (Zip Code)

----------
(4) Insert here the number of shares called for on the face of this Warrant
Certificate (or, in the case of a partial exercise, the portion thereof as to
which the Warrants evidenced by this Warrant Certificate are being exercised),
in either case without making any adjustment for any stock or other securities
or property or cash which, pursuant to the adjustment provisions of the Warrants
evidenced by this Warrant Certificate, may be delivered upon exercise. In the
case of a partial exercise, a new Warrant Certificate will be issued and
delivered, representing the unexercised portion of the Warrants, to the holder
surrendering this Warrant Certificate.

                                      -11-
<Page>

                              SCHEDULE OF EXCHANGES

The following exchanges of a part of this Global Warrant for Physical Warrants
(or of Physical Warrants for an interest in the Global Warrant) have been made:

<Table>
<Caption>
                                                               Number of
                     Amount of           Amount of         Warrants of this
                    decrease in         increase in         Global Warrant          Signature of
                     Number of           Number of          following such           authorized
 Date of          Warrants this       Warrants of this       decrease (or            officer of
Exchange          Global Warrant       Global Warrant          increase)            Warrant Agent
----------        --------------      ----------------     -----------------        --------------
<S>               <C>                 <C>                  <C>                      <C>

</Table>

                                      -12-

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