<PAGE>

                                                                     EXHIBIT 4.3

                                                            WARRANT NO. ________

THIS WARRANT AND THE SECURITIES REPRESENTED BY, OR ACQUIRABLE UPON CONVERSION OR
EXERCISE OF SECURITIES EVIDENCED BY, THIS WARRANT HAVE NOT BEEN REGISTERED UNDER
THE SECURITIES ACT OF 1933, AS AMENDED, AND MAY NOT BE OFFERED, SOLD, PLEDGED OR
OTHERWISE TRANSFERRED IN THE ABSENCE OF AN EFFECTIVE REGISTRATION STATEMENT
UNDER SAID ACT UNLESS THE ISSUER OF THIS WARRANT RECEIVES AN OPINION OF LEGAL
COUNSEL REASONABLY ACCEPTABLE TO THE ISSUER AND ITS LEGAL COUNSEL THAT SUCH SALE
IS EXEMPT FROM REGISTRATION UNDER SUCH ACT AND IS IN COMPLIANCE WITH APPLICABLE
STATE SECURITIES OR BLUE SKY LAWS UNLESS SUCH REGISTRATION IS NOT REQUIRED.

                                SERIES D WARRANT

                  TO PURCHASE _______ SHARES OF COMMON STOCK OF

                     VASCO DATA SECURITY INTERNATIONAL, INC.

         THIS IS TO CERTIFY THAT ____________________, or registered assigns
(the "HOLDER"), is entitled, at any time prior to the Expiration Date (as
hereinafter defined), to purchase from VASCO Data Security International, Inc. a
Delaware corporation (the "COMPANY"), the Warrant Shares (as hereinafter defined
and subject to adjustment as provided herein), in whole or in part, at a
purchase price of $_______ per share (initially and as adjusted, if at all,
pursuant to the terms and conditions of this Warrant, the "EXERCISE PRICE"), all
on and subject to the terms and conditions hereinafter set forth.

         1. DEFINITIONS. As used in this Warrant, the following terms have the
respective meanings set forth below:

         "AFFILIATE" means any Person that, directly or indirectly through one
or more intermediaries, controls or is controlled by or is under common control
with a Person, as such terms are used in and construed under Rule 144 under the
Securities Act. With respect to a Holder of Warrants, any investment fund or
managed account that is managed on a discretionary basis by the same investment
manager as such Holder will be deemed to be an Affiliate of such Holder.

         "APPRAISED VALUE" means, in respect of any share of Common Stock on any
date herein specified, the fair saleable value of such share of Common Stock
(determined without giving effect to the discount for (i) a minority interest or
(ii) any lack of liquidity of the Common Stock or to the fact that the Company
may have no class of equity registered under the Exchange Act) as of the last
day of the most recent fiscal month ending prior to such date specified, based
on the value of the Company, as determined by a nationally recognized investment
banking firm selected by the Company's Board of Directors and having no prior
relationship with the Company.


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         "BUSINESS DAY" means any day that is not a Saturday or Sunday or a day
on which banks are required or permitted to be closed in the State of Delaware.

         "CHANGE OF CONTROL" means the (i) acquisition by an individual or legal
entity or group (as defined in Rule 13d-3 of the Exchange Act) of more than
one-half of the voting rights or equity interests in the Company; (ii) sale,
conveyance, or other disposition of all or substantially all of the assets,
property or business of the Company, (iii) reorganization of the Company's
capital, or (iv) merger into or consolidation with any other corporation (other
than a wholly owned subsidiary corporation) or effectuation of any transaction
or series of related transactions where holders of the Company's voting
securities prior to such transaction or series of transactions fail to continue
to hold at least 50% of the voting power of the Company.

         "CLOSING DATE" means September 10, 2003.

         "COMMISSION" means the Securities and Exchange Commission or any other
federal agency then administering the Securities Act and other federal
securities laws.

         "COMMON STOCK" means (except where the context otherwise indicates) the
class of common stock, $0.001 par value per share, of the Company as constituted
on the Closing Date, and any capital stock into which such Common Stock may
thereafter be changed or converted, and shall also include (i) capital stock of
the Company of any other class (regardless of how denominated) issued to the
holders of shares of Common Stock upon any reclassification thereof which is
also not preferred as to dividends or assets on liquidation over any other class
of stock of the Company and which is not subject to redemption and (ii) shares
of common stock of any successor or acquiring corporation received by or
distributed to the holders of Common Stock in the circumstances contemplated by
Section 4.C.

         "EXCHANGE ACT" means the Securities Exchange Act of 1934, as amended,
and the rules and regulations of the Commission thereunder, all as the same
shall be in effect from time to time.

         "EXERCISE PERIOD" means the period during which this Warrant is
exercisable pursuant to Section 2.a.

         "EXPIRATION DATE" means September 10, 2008.

         "MARKET PRICE" means, in respect of any share of Common Stock, if there
shall not be a public market for the Common Stock on the Business Day
immediately preceding the Closing Date, the higher of (a) the book value per
share of Common Stock on such date and (b) the Appraised Value per share of
Common Stock on such date, or if there shall then be a public market for the
Common Stock on the Business Day immediately preceding the Closing Date, the
higher of (a) the book value per share of Common Stock on such date, and (b) the
average of the daily market prices for 20 consecutive Trading Days immediately
preceding such date. The daily market price for each such Trading Day shall be
(i) the last sale price on such day on the principal stock exchange on which
such Common Stock is then listed or admitted to trading (including Nasdaq), (ii)
if no sale takes place on such day on any such exchange, the average of the last
reported closing bid and asked prices on such day as officially quoted on any
such exchange (including Nasdaq), (iii) if the Common Stock is not then listed
or admitted to trading


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<PAGE>


on any stock exchange, the average of the last reported closing bid and asked
prices on such day in the over-the-counter market, as furnished by Nasdaq or the
National Quotation Bureau, Inc., (iv) if neither such corporation at the time is
engaged in the business of reporting such prices, as furnished by any similar
firm then engaged in such business reasonably acceptable to holders of at least
a majority of the then outstanding shares of the Company's Series D 5%
Cumulative Convertible Voting Preferred Stock, or (v) if there is no such firm,
as furnished by any member of the NASD selected mutually by the Holder and the
Company or, if they cannot agree upon such selection, as selected by two such
members of the NASD, one of which shall be selected by the Holder and one of
which shall be selected by the Company.

         "NASD" means the National Association of Securities Dealers, Inc., or
any successor corporation thereto.

         "NASDAQ" means the Nasdaq Stock Market, Inc.

         "OTHER PROPERTY" has the meaning set forth in Section 4.b.i.

         "PERSON" means any individual, sole proprietorship, partnership, joint
venture, trust, incorporated organization, association, corporation, limited
liability company, institution, public benefit corporation, entity or government
(whether federal, state, county, city, municipal or otherwise, including,
without limitation, any instrumentality, division, agency, body or department
thereof).

         "SECURITIES ACT" means the Securities Act of 1933, as amended, and the
rules and regulations of the Commission thereunder, all as the same shall be in
effect at the time.

         "TRADING DAY" means any day on which the primary market on which shares
of Common Stock are listed is open for trading.

         "TRANSFER" means any disposition of any Warrant or Warrant Shares or of
any interest in either thereof, which would constitute a sale thereof within the
meaning of the Securities Act.

         "WARRANTS" means this Warrant and all warrants issued upon transfer,
division or combination of, or in substitution for, any thereof. All Warrants
shall at all times be identical as to terms and conditions and date, except as
to the number of shares of Common Stock for which they may be exercised.

         "WARRANT PRICE" means an amount equal to (i) the number of shares of
Common Stock being purchased upon exercise of this Warrant pursuant to Section
2.a, multiplied by (ii) the Exercise Price.

         "WARRANT SHARES" means any one or more of the 600,000 shares of Common
Stock to be purchased upon the exercise hereof, subject to adjustment as
provided herein.

         2. EXERCISE OF WARRANT.

                  a. Manner of Exercise.


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<PAGE>


                           i. From and after the Closing Date, and until 5:00
P.M., Delaware time, on the Expiration Date (the "EXERCISE PERIOD"), the Holder
may exercise this Warrant, on any Business Day, for all or any part of the
number of Warrant Shares purchasable hereunder.

                           ii. In order to exercise this Warrant, in whole or in
part, the Holder shall deliver to the Company at its principal office or at the
office or agency designated by the Company pursuant to Section I, (i) a written
notice of Holder's election to exercise this Warrant, which notice shall specify
the number of Warrant Shares to be purchased, (ii) payment of the Warrant Price
as provided herein, and (iii) this Warrant. Such notice shall be substantially
in the form of the subscription form (the "SUBSCRIPTION FORM") appearing at the
end of this Warrant as Exhibit A, duly executed by the Holder or its agent or
attorney. Upon receipt thereof, the Company shall, as promptly as reasonably
practicable, and in any event within five (5) Business Days thereafter (the
"DELIVERY PERIOD"), execute or cause to be executed and deliver or cause to be
delivered to the Holder a certificate or certificates representing the aggregate
number of Warrant Shares issuable upon such exercise, together with cash in lieu
of any fraction of a share, as hereinafter provided. The stock certificate or
certificates so delivered shall be in such denomination or denominations as the
Holder may reasonably request in the notice and shall be registered in the name
of the Holder or such other name as shall be designated in the notice and,
following the date on which the Warrant Shares have been sold and transferred
pursuant to an effective resale registration statement filed with the Commission
or otherwise may be sold by the Holder pursuant to Rule 144(k) promulgated under
the Securities Act (or a successor rule), shall not bear any restrictive legend.
This Warrant shall be deemed to have been exercised and such certificate or
certificates shall be deemed to have been issued, and the Holder or any other
Person so designated to be named therein shall be deemed to have become a Holder
of record of such shares for all purposes, as of the date when the notice,
together with the payment of the Warrant Price and this Warrant, is received by
the Company as described above. If this Warrant shall have been exercised in
part, the Company shall, at the time of delivery of the certificate or
certificates representing Warrant Shares, deliver to the Holder a new Warrant
evidencing the rights of the Holder to purchase the unpurchased shares of Common
Stock called for by this Warrant, which new Warrant shall in all other respects
be identical with this Warrant, or at the request of the Holder, appropriate
notation may be made on this Warrant and the same returned to the Holder.

                           iii. Payment of the Warrant Price may be made at the
option of the Holder by: (i) certified or official bank check payable to the
order of the Company, or (ii) wire transfer to the account of the Company. All
shares of Common Stock issuable upon the exercise of this Warrant pursuant to
the terms hereof shall be validly issued and, upon payment of the Warrant Price,
shall be fully paid and nonassessable and not subject to any preemptive rights.
The Company shall pay all expenses in connection with, and all transfer, stamp
or similar taxes and other governmental charges that may be imposed with respect
to, the issue or delivery thereof, provided, however, that the Company shall not
be required to pay any tax which may be payable in respect of any transfer
involved in the issuance of any certificates for Warrant Shares or Warrants in a
name other than the name of the Holder.

                           iv. Prior to the exercise of this Warrant, the Holder
shall not be entitled to any rights as a stockholder of the Company with respect
to the Warrant Shares,


                                      -4-
<PAGE>


including, without limitation, the right to vote such Warrant Shares, receive
dividends or other distributions thereon or to be notified of stockholder
meetings, except as set forth herein.

                           v. If the Company's transfer agent is participating
in the Depository Trust Company ("DTC") Fast Automated Securities Transfer
program, and so long as the certificates therefor do not bear a legend (pursuant
to the terms of that certain Preferred Stock and Warrant Purchase Agreement,
dated September 10, 2003, by and among the Company and the signatories thereto
(the "PURCHASE AGREEMENT"), the Company shall cause its transfer agent to
electronically transmit the Warrant Shares so purchased to the Holder or the
Holder's designee by crediting the account of the Holder or the Holder's
designee or its respective nominee with DTC through its Deposit Withdrawal Agent
Commission system ("DTC TRANSFER"). If the aforementioned conditions to a DTC
Transfer are not satisfied, the Company shall deliver to the Holder or the
Holder's designee physical certificates representing the Warrant Shares so
purchased. Notwithstanding the foregoing, the Holder or the Holder's designee
may instruct the Company to deliver to the Holder or such designee physical
certificates representing the Warrant Shares so purchased in lieu of delivering
such shares by way of DTC Transfer.

                           vi. If, at any time, a Holder of this Warrant submits
this Warrant, a Subscription Form and payment to the Company of the Exercise
Price for each of the Warrant Shares specified in the Subscription Form
(including pursuant to a Cashless Exercise), and the Company fails for any
reason (other than the reasons contemplated by Section 2.a hereof) to deliver,
on or prior to the fourth business day following the expiration of the Delivery
Period for such exercise, the number of shares of Common Stock to which the
Holder is entitled upon such exercise (an "EXERCISE DEFAULT"), then the Company
shall pay to the Holder payments ("EXERCISE DEFAULT PAYMENTS") for an Exercise
Default in the amount of (i) (N/365), multiplied by (ii) the amount by which the
Market Price of the Common Stock on the date the Exercise Agreement giving rise
to the Exercise Default is transmitted in accordance with this Section 2 (the
"EXERCISE DEFAULT DATE") exceeds the Exercise Price in respect of such Warrant
Shares, multiplied by (iii) the number of shares of Common Stock the Company
failed to so deliver in such Exercise Default, multiplied by (iv) .24, where N
equals the number of days from the Exercise Default Date to the date that the
Company effects the full exercise of this Warrant which gave rise to the
Exercise Default. The accrued Exercise Default Payment for each calendar month
shall be paid in cash and shall be made to the Holder by the fifth day of the
month following the month in which it has accrued. Nothing herein shall limit
the Holder's right to pursue actual damages for the Company's failure to
maintain a sufficient number of authorized shares of Common Stock as required
pursuant to the terms of Section 6 hereof or to otherwise issue shares of Common
Stock upon exercise of this Warrant in accordance with the terms hereof, and the
Holder shall have the right to pursue all remedies available at law or in equity
(including a decree of specific performance and/or injunctive relief).

                  b. Restrictions on Exercise Amount. Notwithstanding any
contrary or inconsistent provision hereof, the Holder may not acquire a number
of Warrant Shares to the extent that, upon such exercise, the number of shares
of Common Stock then owned of record by such Holder and its Affiliates and any
other Persons or entities whose record ownership of Common Stock would be
aggregated with the Holder's for purposes of Section 13(d) of the Exchange Act
(including shares held by any "group" of which the Holder is a member) exceeds
4.95% of the total number of shares of Common Stock then issued and outstanding
(such


                                      -5-
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limitation being herein referred to as the "BENEFICIAL OWNERSHIP CAP"). For
purposes hereof, "group" has the meaning set forth in Section 13(d) of the
Exchange Act and applicable regulations of the Commission, and the percentage
held by the Holder shall be determined in a manner consistent with the
provisions of Section 13(d) of the Exchange Act. The restriction contained in
this Section 2.b may not be altered, amended, deleted or changed in any manner
whatsoever unless the holders of a majority of the outstanding shares of Common
Stock and the Holder hereof shall approve, in writing, such alteration,
amendment, deletion or change.

         3. TRANSFER, DIVISION AND COMBINATION.

                  a. Transfer. The Warrants and the Warrant Shares may not be
transferred or assigned in whole or in part without compliance with all
applicable federal and state securities laws by the transferor and the
transferee (including the delivery of investment representation letters and
legal opinions reasonably satisfactory to the Company, if such are requested by
the Company; provided that such letters and legal opinions shall not be
unreasonably requested with respect to a transfer to an Affiliate of the Holder)
and any stockholders agreement to which the transferor is a party. Subject to
the foregoing, Transfer of this Warrant and all rights hereunder, in whole or in
part, shall be registered on the books of the Company to be maintained for such
purpose, upon surrender of this Warrant at the principal office of the Company
referred to in Section 10.b or the office or agency designated by the Company
pursuant to Section 9, together with a written assignment of this Warrant
substantially in the form of Exhibit B hereto duly executed by the Holder or its
agent or attorney and funds sufficient to pay any transfer taxes payable upon
the making of such Transfer. Upon such surrender and, if required, such payment,
the Company shall execute and deliver a new Warrant or Warrants in the name of
the assignee or assignees and in the denomination specified in such instrument
of assignment, and shall issue to the assignor a new Warrant evidencing the
portion of this Warrant not so assigned, and this Warrant shall promptly be
cancelled. The acceptance of the new Warrant or Warrants by the transferee
thereof shall be deemed the acceptance by such transferee of all of the rights
and obligations of a Holder. Following a transfer that complies with the
requirements of this Section 3.a, the Warrant may be exercised by a new Holder
for the purchase of shares of Common Stock regardless of whether the Company
issued or registered a new Warrant on the books of the Company.

                  b. Prohibited Transfers. Notwithstanding anything to the
contrary herein, the Holder shall at all times be prohibited from transferring
any Warrant and any Warrant Shares to any Person who, at the time of such
determination, is currently engaging, or is reasonably likely to engage, in the
same or a substantially similar business as that of the Company.

                  c. Restrictive Legend. Each certificate for Warrant Shares
initially issued upon the exercise of this Warrant unless such Warrant Shares
may otherwise be sold by the Holder pursuant to Rule 144(k) promulgated under
the Securities Act (or a successor rule), each certificate for Warrant Shares
issued to any subsequent transferee of any such certificate, shall be stamped or
otherwise imprinted with a legend in substantially the following form:

                  "THE SECURITIES REPRESENTED BY, OR ACQUIRABLE UPON CONVERSION
                  OR EXERCISE OF SECURITIES EVIDENCED BY, THIS CERTIFICATE HAVE
                  NOT BEEN


                                      -6-
<PAGE>


                  REGISTERED UNDER THE SECURITIES ACT OF 1933, AS AMENDED, AND
                  MAY NOT BE OFFERED, SOLD, PLEDGED OR OTHERWISE TRANSFERRED IN
                  THE ABSENCE OF AN EFFECTIVE REGISTRATION STATEMENT UNDER SAID
                  ACT UNLESS THE ISSUER OF THIS CERTIFICATE RECEIVES AN OPINION
                  OF LEGAL COUNSEL REASONABLY ACCEPTABLE TO THE ISSUER AND ITS
                  LEGAL COUNSEL THAT SUCH SALE IS EXEMPT FROM REGISTRATION UNDER
                  SUCH ACT AND IS IN COMPLIANCE WITH APPLICABLE STATE SECURITIES
                  OR BLUE SKY LAWS UNLESS SUCH REGISTRATION IS NOT REQUIRED."

                  d. Division and Combination; Expenses; Books. This Warrant may
be divided or combined with other Warrants upon presentation hereof at the
aforesaid office or agency of the Company, together with a written notice
specifying the names and denominations in which new Warrants are to be issued,
signed by the Holder or its agent or attorney. Subject to compliance with
Section 3.a as to any transfer which may be involved in such division or
combination, the Company shall execute and deliver a new Warrant or Warrants in
exchange for the Warrant or Warrants to be divided or combined in accordance
with such notice. The Company shall prepare, issue and deliver at its own
expense the new Warrant or Warrants under this Section 3. The Company agrees to
maintain, at its aforesaid office or agency, books for the registration and the
registration of transfer of the Warrants.

         4. ADJUSTMENTS. The number of shares of Common Stock for which this
Warrant is exercisable, and the Exercise Price, shall be subject to adjustment
from time to time as set forth in this Section 4. The Company shall give the
Holder notice of any event described below which requires an adjustment pursuant
to this Section 4 in accordance with Sections 5.a and 5.b.

                  a. Stock Dividends, Subdivisions and Combinations. If at any
time while this Warrant is outstanding the Company shall:

                           i. take a record of the holders of its Common Stock
for the purpose of entitling them to receive a dividend payable in, or other
distribution of, additional shares of Common Stock,

                           ii. subdivide its outstanding shares of Common Stock
into a larger number of shares of Common Stock, or

                           iii. combine its outstanding shares of Common Stock
into a smaller number of shares of Common Stock, then:

                                 (1) the number of shares of Common Stock
acquirable upon exercise of this Warrant immediately after the occurrence of any
such event shall be adjusted to equal the number of shares of Common Stock which
a record holder of the same number of shares of Common Stock that would have
been acquirable under this Warrant immediately prior


                                      -7-
<PAGE>


to the occurrence of such event would own or be entitled to receive after the
happening of such event, and

                                 (2) the Exercise Price shall be adjusted to
equal:

                                    (A) the Exercise Price in effect immediately
prior to the occurrence of such event multiplied by the number of shares of
Common Stock into which this Warrant is exercisable immediately prior to the
adjustment, divided by

                                    (B) the number of shares of Common Stock
into which this Warrant is exercisable immediately after such adjustment.

Any adjustment made pursuant to clause (i) of this Section 4.a shall become
effective immediately after the record date for the determination of
stockholders entitled to receive such dividend or distribution, and any
adjustment pursuant to clauses (ii) or (iii) of this Section 4.a shall become
effective immediately after the effective date of such subdivision or
combination.

                  b. Reorganization, Reclassification, Merger, Consolidation or
Disposition of Assets.

                           i. If, during the Exercise Period, there shall occur
a Change of Control and, pursuant to the terms of such Change of Control, shares
of common stock of the successor or acquiring corporation, or any cash, shares
of stock or other securities or property of any nature whatsoever (including
warrants or other subscription or purchase rights) in addition to or in lieu of
common stock of the successor or acquiring corporation ("OTHER PROPERTY"), are
to be received by or distributed to the holders of Common Stock, then the Holder
shall have the right thereafter to receive, upon the exercise of the Warrant,
the number of shares of common stock of the successor or acquiring corporation
or of the Company, if it is the surviving corporation, and the Other Property
receivable upon or as a result of such Change of Control by a holder of the
number of shares of Common Stock into which this Warrant is exercisable
immediately prior to such event.

                           ii. In case of any such Change of Control, the
successor or acquiring corporation (if other than the Company) shall expressly
assume the due and punctual observance and performance of each and every
covenant and condition contained in this Warrant to be performed and observed by
the Company and all the obligations and liabilities hereunder, subject to such
modifications as may be deemed appropriate (as determined by resolution of the
Board of Directors of the Company) in order to provide for adjustments of shares
of the Common Stock into which this Warrant is exercisable which shall be as
nearly equivalent as practicable to the adjustments provided for in this Section
4.

                  c. Other Action Affecting Common Stock. In case at any time or
from time to time the Company shall take any action in respect of its Common
Stock, then, unless such action will not have a materially adverse effect upon
the rights of the Holder, the number of shares of Common Stock or other stock
into which this Warrant is exercisable and/or the Exercise Price shall be
adjusted in such manner as may be equitable in the circumstances.


                                      -8-
<PAGE>


                  d. Certain Limitations. Notwithstanding anything herein to the
contrary, the Company agrees not to enter into any transaction which, by reason
of any adjustment hereunder, would cause the Exercise Price to be less than the
par value per share of Common Stock.

                  e. Stock Transfer Taxes. The issue of stock certificates upon
exercise of this Warrant shall be made without charge to the Holder for any tax
in respect of such issue.

                  f. Fractional Interests. The Company shall not be required to
issue a fractional share of Common Stock upon exercise of any Warrant. If an
adjustment made pursuant to this Section 4 entitles the Holder to any fraction
of a share, such fraction shall be rounded to the nearest whole number and the
Holder shall be entitled to that number of shares.

         5. NOTICES TO WARRANT HOLDERS.

                  a. Certificate as to Adjustments. Upon the occurrence, if any,
of each adjustment or readjustment of the Exercise Price, or the number of
shares of Common Stock and the amount, if any of Other Property which at the
time would be received upon exercise of the Warrants owned by such Holder, the
Company, at its expense, shall promptly compute such adjustment or readjustment
in accordance with the terms hereof and prepare and furnish to the Holder a
certificate setting forth such adjustment or readjustment and showing in detail
the facts upon which such adjustment or readjustment is based. The Company
shall, upon the reasonable written request at any time of the Holder, furnish or
cause to be furnished to such Holder a like certificate setting forth (i) such
adjustments and readjustments, (ii) the Exercise Price at the time in effect and
(iii) the number of shares of Common Stock and the amount, if any, or Other
Property which at the time would be received upon the exercise of Warrants owned
by such Holder.

                  b. Notice of Corporate Action. If at any time:

                           i. the Company shall take a record of the holders of
its Common Stock for the purpose of entitling them to receive a dividend or
other distribution, or any right to subscribe for or purchase any evidences of
its indebtedness, any shares of stock of any class or any other securities or
property, or to receive any other right, or

                           ii. there shall be any capital reorganization of the
Company, any reclassification or recapitalization of the capital stock of the
Company or any consolidation or merger of the Company with, or any sale,
transfer or other disposition of all or substantially all the property, assets
or business of the Company to, another corporation, or

                           iii. there shall be a voluntary or involuntary
dissolution, liquidation or winding up of the Company;

then, in any one or more of such cases, the Company shall give to the Holder (i)
at least 15 days' prior written notice of the record date that shall be selected
for such dividend, distribution or right or for determining rights to vote in
respect of any such reorganization, reclassification, merger, consolidation,
sale, transfer, disposition, dissolution, liquidation or winding up, and (ii) in
the case of any such reorganization, reclassification, merger, consolidation,
sale, transfer, disposition, dissolution, liquidation or winding up, at least 15
days' prior written notice of the


                                      -9-
<PAGE>


date when the same shall take place. Such notice in accordance with the
foregoing clause also shall specify (1) the date on which any such record is to
be taken for the purpose of such dividend, distribution or right, the date on
which the holders of Common Stock shall be entitled to any such dividend,
distribution or right, and the amount and character thereof, and (2) the date on
which any such reorganization, reclassification, merger, consolidation, sale,
transfer, disposition, dissolution, liquidation or winding up is to take place
and the time, if any such time is to be fixed, as of which the holders of Common
Stock shall be entitled to exchange their shares of Common Stock for securities
or Other Property deliverable upon such reorganization, reclassification,
merger, consolidation, sale, transfer, disposition, dissolution, liquidation or
winding up. Each such written notice shall be sufficiently given if addressed to
the Holder at the last address of the Holder appearing on the books of the
Company and delivered in accordance with Section 10.b. The failure to give any
notice required by this Section 5.b shall not invalidate any such corporate
action.

                  c. Notice to Stockholders. The Holder shall be entitled to the
same rights to receive notice of corporate action as any holder of Common Stock.
Subject to the foregoing, the Holder, as such, shall not be entitled to vote or
receive dividends or be deemed the holder of Common Stock or any other
securities of the Company that may at any time be issuable on the exercise
hereof for any purpose, nor shall anything contained herein be construed to
confer upon the Holder, as such, any of the rights of a stockholder of the
Company or any right to vote for the election of directors or upon any matter
submitted to stockholders at any meeting thereof, or to give or withhold consent
to any corporate action (whether upon any recapitalization, issuance of stock,
reclassification of stock, change of par value, or change of stock to no par
value, consolidation, merger, conveyance, or otherwise) or to receive dividends
or subscription rights or otherwise until this Warrant shall have been exercised
as provided herein.

         6. RESERVATION AND AUTHORIZATION OF COMMON STOCK: REGISTRATION WITH
APPROVAL OF ANY GOVERNMENTAL AUTHORITY. From and after the Closing Date until
the Expiration Date, the Company shall at all times reserve and keep available
for issue upon the exercise of the Warrants such number of its authorized but
unissued shares of Common Stock as will be sufficient to permit the exercise in
full of all outstanding Warrants. All shares of Common Stock which shall be so
issuable, when issued upon exercise of any Warrant and payment therefor in
accordance with the terms of such Warrant, shall be duly and validly issued and
fully paid and nonassessable, and not subject to preemptive rights.

         7. TAKING OF RECORD; STOCK AND WARRANT TRANSFER BOOKS. In the case of
all dividends or other distributions by the Company to the holders of its Common
Stock with respect to which any provision of Section 4 refers to the taking of a
record of such holders, the Company will in each such case take such a record
and will take such record as of the close of business on a Business Day. The
Company will not at any time, except upon dissolution, liquidation or winding up
of the Company, close its stock transfer books or Warrant transfer books so as
to result in preventing or delaying the exercise or transfer of any Warrant.

         8. LOSS OR MUTILATION. Upon receipt by the Company from the Holder of
evidence reasonably satisfactory to the Company of the ownership of and the
loss, theft, destruction or mutilation of this Warrant and indemnity reasonably
satisfactory to the Company


                                      -10-
<PAGE>


(it being understood that the written agreement of the original Holder shall be
sufficient indemnity) and in case of mutilation upon surrender and cancellation
hereof, the Company, at its expense, will execute and deliver in lieu hereof a
new Warrant of like tenor to the Holder; provided, however, that in the case of
mutilation, no indemnity shall be required if this Warrant in identifiable form
is surrendered to the Company for cancellation. Applicants for a replacement
Warrant under such circumstances shall also comply with such other reasonable
regulations and procedures and pay such other reasonable charges as the Company
may prescribe.

         9. OFFICE OF THE COMPANY. As long as any of the Warrants remain
outstanding, the Company shall maintain an office or agency (which may be the
principal executive offices of the Company) where the Warrants may be presented
for exercise, registration of transfer, division or combination as provided in
this Warrant.

         10. MISCELLANEOUS.

                  a. Nonwaiver and Expenses. No course of dealing or any delay
or failure to exercise any right hereunder on the part of the Holder shall
operate as a waiver of such right or otherwise prejudice Holder's rights, powers
or remedies. If the Company fails to make, when due, any payments provided for
hereunder, or fails to comply with any other provision of this Warrant, the
Company shall pay to the Holder such amounts as shall be sufficient to cover any
costs and expenses including, but not limited to, reasonable attorneys' fees,
including those of appellate proceedings, incurred by the Holder in collecting
any amounts due pursuant hereto or in otherwise enforcing any of its rights,
powers or remedies hereunder.

                  b. Notice Generally. All notices, requests, demands or other
communications provided for herein shall be in writing and shall be deemed to
have been given the next Business Day after being deposited with a nationally
recognized overnight courier such as Federal Express, or, when personally
delivered, or successfully sent by facsimile transmission as evidenced by a fax
machine confirmation report thereof, addressed, as the case may be, to the
Holder at the address on the books and records of the Company; or to the
Company, VASCO Data Security International, Inc., 1901 South Meyers Road, Suite
210, Oakbrook Terrace, Illinois 60181, Att'n: Clifford K. Bown, Chief Financial
Officer, Fax No. 630.932.8852; with a copy to Pepper Hamilton LLP, 600
Fourteenth Street, N.W., Washington, D.C. 20005-2004, Fax No. 202.220.1665,
Att'n Robert B. Murphy, Esquire, or to such other Person or address as either
party shall designate to the other from time to time in writing forwarded in
like manner.

                  c. Successors and Assigns. Subject to compliance with the
provisions of Section 3.a, this Warrant and the rights evidenced hereby shall
inure to the benefit of and be binding upon the successors of the Company and
the successors and assigns of the Holder. The provisions of this Warrant are
intended to be for the benefit of all Holders from time to time of this Warrant,
and shall be enforceable by any such Holder, but nothing in this Warrant shall
be construed to give any Person, other than the Company and the Holder and their
respective successors and assigns, any legal or equitable right, remedy or cause
under this Warrant.

                  d. Amendment. This Warrant may be modified or amended or the
provisions of this Warrant waived with the written consent of the Company and
the Holder.

                                      -11-
<PAGE>

                  e. Severability. Wherever possible, each provision of this
Warrant shall be interpreted in such manner as to be effective and valid under
applicable law, but if any provision of this Warrant shall be prohibited by or
invalid under applicable law, such provision shall be modified to the extent of
such prohibition or invalidity, without invalidating the remainder of such
provision or the remaining provisions of this Warrant.

                  f. Headings. The headings used in this Warrant are for the
convenience of reference only and shall not, for any purpose, be deemed a part
of this Warrant

                  g. Governing Law. This Warrant and the transactions
contemplated hereby shall be deemed to be consummated in the State of Delaware
and shall be governed by and interpreted in accordance with the local laws of
the State of Delaware without regard to the provisions thereof relating to
conflict of laws.


      [REMAINDER OF PAGE LEFT INTENTIONALLY BLANK. SIGNATURE PAGES FOLLOW].


                                      -12-
<PAGE>

            IN WITNESS WHEREOF, the Company has caused this Series D Warrant to
be executed by its duly authorized officer and attested by its Secretary.

Dated: September 10, 2003               VASCO DATA SECURITY INTERNATIONAL. INC.


                                        By:
                                            ------------------------------------
                                        Name:  T. Kendall Hunt
                                        Title: Chairman of the Board and Chief
                                               Executive Officer

Attest:


By:
   --------------------------------
Name:  Clifford K. Bown
Title: Corporate Secretary


                                      -13-
<PAGE>

                                    EXHIBIT A

                                SUBSCRIPTION FORM

                 [To be executed only upon exercise of Warrant]

The undersigned registered owner of this Warrant hereby exercises this Warrant
for the purchase of _____________________ shares of Common Stock of VASCO Data
Security International, Inc., a Delaware corporation (the "Company"), and
herewith makes payment therefor, all at the price and on the terms and
conditions specified in this Warrant and requests that certificates for the
shares of Common Stock hereby purchased (and any securities or Other Property
issuable upon such exercise) be issued in the name of and delivered to and whose
address is _______________. And, if such shares of Common Stock shall not
include all of the shares of Common Stock issuable as provided in this Warrant,
that a new Warrant of like tenor and date for the balance of the shares of
Common Stock issuable hereunder be delivered to the undersigned.

As of the date hereof, and assuming the accuracy of all information filed by the
Company with the Securities and Exchange Commission, the undersigned Holder
hereby certifies that the exercise of the referenced Warrant for the number of
Warrant Shares herein indicated will not put the undersigned Holder out of
compliance with the Beneficial Ownership Cap (as defined in the Warrant).

By signing below, the Holder warrants and represents that the Holder is an
"accredited investor" as that term is defined under Regulation D of the
Securities and Exchange Commission promulgated under the Securities Act of 1933,
as amended.


               --------------------------------------------
               (Name of Registered Owner)

               --------------------------------------------
               (Signature of Registered Owner)

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

               --------------------------------------------
               (City, State and Zip Code)


NOTICE: The signature on this subscription must correspond with the name as
written upon the face of the Warrant.


                                      A-1
<PAGE>

                                    EXHIBIT B

                                 ASSIGNMENT FORM

FOR VALUE RECEIVED the undersigned registered owner of this Warrant for the
purchase of shares of the Common Stock of VASCO Data Security International,
Inc., a Delaware corporation (the "Company"), hereby sells, assigns and
transfers unto the Assignee named below all of the rights of the undersigned
under this Warrant, with respect to the number of shares of Common Stock set
forth below:

       Name and Address of Assignee:
                                       ------------------------------------
                                       ------------------------------------
                                       ------------------------------------


       No. of Shares of Common Stock:
                                       -----------------------


and does hereby irrevocably constitute and appoint _____________________________
attorney-in-fact to register such transfer on the books of the Company,
maintained for the purpose, with full power of substitution in the premises.

                           Dated:
                                       ------------------------------------

                           Print Name:
                                       ------------------------------------

                           Signature:
                                       ------------------------------------

                           Witness:
                                       ------------------------------------


NOTICE: The signature on this assignment must correspond with the name as
written upon the face of the Warrant in every particular.


                                      B-1