Document:

<PAGE>   1
                                                                    EXHIBIT 4.2

[BLUE BORDER DESIGN]

                             [FRONT OF CERTIFICATE]

      NUMBER             [WITNESS SYSTEMS, INC. LOGO]          SHARES
                             WITNESS SYSTEMS, INC.

<TABLE>

<S>                        <C>                                                            <C>
COMMON STOCK                                                                                 SEE REVERSE FOR
$0.01 PAR VALUE            INCORPORATED UNDER THE LAWS OF THE STATE OF DELAWARE           CERTAIN DEFINITIONS
</TABLE>

                                                              CUSIP 977424-10-D

THIS CERTIFIES THAT___________________________________________________[SPECIMEN]

_____________________
IS THE OWNER OF _______________________________________________________________
          FULLY PAID AND NON-ASSESSABLE SHARES OF THE COMMON STOCK OF
                             WITNESS SYSTEMS, INC.
transferable on the books of the Corporation in person or by duly authorized
attorney, upon the surrender of this certificate properly endorsed. This
certificate is not valid unless countersigned by the Transfer Agent and
registered by the Registrar.

   Witness the facsimile signatures of its duly authorized officers and
facsimile of its corporate seal.

Dated:

<TABLE>

<S>                                 <C>                         <C>
/s/ Jon W. Ezrine                   [WITNESS SYSTEMS, INC.      /s/ David Gould
---------------------------         CORPORATE SEAL              ------------------------------------------
Secretary                           DELAWARE]                   Chairman, President and Chief Executive
Officer
</TABLE>

COUNTERSIGNED AND REGISTERED:

SUNTRUST BANK, ATLANTA
TRANSFER AGENT AND REGISTRAR

BY
  -------------------------
     AUTHORIZED SIGNATURE

<PAGE>   2

                             [BACK OF CERTIFICATE]

                             WITNESS SYSTEMS, INC.

         The Corporation will furnish without charge to each shareholder who so
requests a statement or summary or summary of the powers, designations,
preferences and relative, participating, optional or other special rights of
each class of stock or series thereof which the Corporation is authorized to
issue and of the qualifications, limitations or restrictions of such
preferences and/or rights. Such request may be made to the office of the
Secretary of the Corporation or the Transfer Agent named on the face of this
Certificate.

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

<TABLE>

<S>                <C>                                         <C>
    TEN COM        -  as tenants in common                     UNIF GIFT MIN ACT- ___________Custodian

    TEN ENT        -  as tenants by the entireties                               -
                                                                                 (Cust)
                                                                                 Minor)
    JT TEN         -  as joint  tenants  with the right                          under the Uniform Gifts to
                      of (s) survivorship (s) and (s) not  as                    Minors Act ________________
                      tenants in common                                                          (State)
</TABLE>

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

For value received, ______________________________________________ hereby sell,

assign and transfer unto ________________  [PLEASE INSERT SOCIAL SECURITY OR
                                           OTHER IDENTIFYING NUMBER OF ASSIGNEE]

_______________________________________________________________________________
  (PLEASE PRINT OR TYPEWRITE NAME AND ADDRESS, INCLUDING ZIP CODE OF ASSIGNEE)

_______________________________________________________________________________

_________________________________________________________________________ Shares
of the common stock represented by the within Certificate, and do hereby
irrevocably constitute and appoint ___________________________________ Attorney
to transfer the said stock on the books of the within named Corporation with
the full power of substitution in the premises.

Dated ________________     ____
                                         ______________________________________
                                NOTICE:  THE SIGNATURE TO THIS ASSIGNMENT MUST
                                         CORRESPOND WITH THE NAME AS  WRITTEN
                                         UPON  THE FACE OF THE  CERTIFICATE
                                         IN EVERY PARTICULAR, WITHOUT ALTERATION
                                         OR ENLARGEMENT OR ANY CHANGE WHATEVER.

                  SIGNATURE(S) GUARANTEED: _____________________________________
                                         THE SIGNATURE(S) SHOULD BE GUARANTEED
                                         BY AN ELIGIBLE GUARANTOR INSTITUTION
                                         (BANKS, STOCKBROKERS, SAVINGS AND
                                         LOAN ASSOCIATIONS AND CREDIT UNIONS
                                         WITH MEMBERSHIP IN AN APPROVED
                                         SIGNATURE GUARANTEE MEDALLION PROGRAM),
                                         PURSUANT TO S.E.C. RULE 17Ad-15.

                                      -2-<PAGE>   1
                                                                   EXHIBIT 10.4

                             WITNESS SYSTEMS, INC.

                              STOCK INCENTIVE PLAN
                         STOCK OPTION GRANT CERTIFICATE

WITNESS SYSTEMS, INC. LOGO

         WITNESS SYSTEMS, INC., a Delaware corporation (the "Company"), hereby
grants to the optionee named below ("Optionee") an option (this "Option") to
purchase the total number of shares shown below of Common Stock of the Company
(the "Shares") at the exercise price per share set forth below (the "Exercise
Price"), subject to all of the terms and conditions on the reverse side of this
Stock Option Grant Certificate and the Witness Systems, Inc. Stock Incentive
Plan (the "Plan"). Unless otherwise defined herein, capitalized terms used
herein shall have the meanings ascribed to them in the Plan. The terms and
conditions set forth on the reverse side hereof and the terms and conditions of
the Plan are incorporated herein by reference.

In Witness Whereof, this Stock Option Grant Certificate has been executed by
the Company by a duly authorized officer as of the date specified hereon.

WITNESS SYSTEMS, INC.

By:____________________________________

Date of Grant: ________________________

Type of Stock Option:
         [_______]         Incentive

         [_______]         Non-Qualified

Shares Subject to Option:       ______
Exercise Price Per Share:      $______
Term of Option:                 ______

Shares subject to issuance under this Option shall be eligible for exercise
according to the vesting schedule selected below and further described in
Section 10 on the reverse of this Stock Option Grant Certificate.

[X]  Four Year Vesting

     Optionee hereby acknowledges receipt of a copy of the Plan, represents
that Optionee has read and understands the terms and provisions of the Plan,
and accepts this Option subject to all the terms and conditions of the Plan and
this Stock Option Grant Certificate. Optionee acknowledges that there may be
adverse tax consequences upon exercise of this Option or disposition of the
Shares and that Optionee should consult a tax adviser prior to such exercise or
disposition.

-------------------------------
Signature of Optionee

-------------------------------
Print Name of Optionee

<PAGE>   2

     1. EXERCISE PERIOD OF OPTION. Subject to the terms and conditions of this
Option and the Plan, and unless otherwise modified by a written modification
signed by the Company and Optionee, this Option may be exercised with respect
to all of the Shares, but only according to the vesting schedule selected on
the reverse of this Stock Option Grant Certificate and as described in Section
10 below, prior to the date which is the last day of the Term set forth on the
face hereof following the date of grant (hereinafter "Expiration Date").

     2. RESTRICTIONS ON EXERCISE. This Option may not be exercised, unless such
exercise is in compliance with the Securities Act of 1933 and all applicable
state securities laws, as they are in effect on the date of exercise, and the
requirements of any stock exchange or national market system on which the
Company's Common Stock may be listed at the time of exercise. Optionee
understands that the Company is under no obligation to register, qualify or
list the Shares with the Securities and Exchange Commission ("SEC"), any state
securities commission or any stock exchange to effect such compliance.

     3. TERMINATION OF OPTION. Except as provided below in this Section, this
Option may not be exercised after the date which is thirty (30) days after
Optionee ceases to perform services for the Company, or any Parent or
Subsidiary. Optionee shall be considered to perform services for the Company,
or any Parent or Subsidiary, for all purposes under this Section and Section 10
hereof, if Optionee is an officer or full-time employee of the Company, or any
Parent or Subsidiary, or if the Board determines that Optionee is rendering
substantial services as a part-time employee, consultant, contractor or advisor
to the Company, or any Parent or Subsidiary. The Board shall have discretion to
determine whether Optionee has ceased to perform services for the Company, or
any Parent or Subsidiary, and the effective date on which such services cease
(the "Termination Date"). Notwithstanding anything contained herein to the
contrary, if the corporate position of Optionee is, at any time, altered or
revised such that Optionee's responsibilities are materially reduced or
decreased for any reason, as determined by the Board in its sole discretion,
the vesting of Shares under Section 10 shall cease, effective as of the date of
such reduction in Optionee's employment responsibilities; provided, however,
except as otherwise provided in this Option and the Plan, Optionee shall have
the right to exercise this Option with respect to Shares which have vested
under Section 10 as of the date of such reduction of Optionee's
responsibilities.

         (a) Termination Generally. If Optionee ceases to perform services for
the Company, or any Parent or Subsidiary, for any reason, except death or
disability (within the meaning of Code Section 22(e)(3)), this Option shall
immediately be forfeited, along with any and all rights or subsequent rights
attached thereto, thirty (30) days following the Termination Date, but in no
event later than the Expiration Date.

         (b) Death or Disability. If Optionee ceases to perform services for
the Company, or any Parent or Subsidiary, as a result of the death or
disability of Optionee (as determined by the Board in its sole discretion),
this Option, to the extent (and only to the extent) that it would have been
exercisable by Optionee on the Termination Date, may be exercised by Optionee
(or, in the event of Optionee's death, by Optionee's legal representative)
within ninety (90) days after the Termination Date, but in no event later than
the Expiration Date.

         (c) No Right to Employment. Nothing in the Plan or this Stock Option
Grant Certificate shall confer on Optionee any right to continue in the employ
of, or other relationship with, the Company, or any Parent or Subsidiary, or
limit in any way the right of the Company, or any Parent or Subsidiary, to
terminate Optionee's employment or other relationship at any time, with or
without cause.

     4.  MANNER OF EXERCISE.

         (a) Exercise Agreement. This Option shall be exercisable by delivery
to the Company of an executed Exercise and Shareholder Agreement ("Exercise
Agreement") in the form of the Exercise Agreement delivered to Optionee, if
applicable, or in such other form as may be approved or accepted by the
Company, which shall set forth Optionee's election to exercise this Option with
respect to some or all of the Shares, the number of Shares being purchased, any
restrictions imposed on the Shares, and such other representations and
agreements as may be required by the Company to comply with applicable
securities laws.

         (b) Exercise Price. Such notice shall be accompanied by full payment
of the Exercise Price for the Shares being purchased. Payment for the Shares
may be made in U.S. dollars in cash (by check) or, where permitted by law and
approved by the Board in its sole discretion: (i) by cancellation of
indebtedness of the Company to Optionee; (ii) by surrender of shares of Common
Stock of the Company that have been owned by

<PAGE>   3

Optionee for more than six (6) months (and which have been paid for within the
meaning of SEC Rule 144, and, if such shares were purchased from the Company by
use of a promissory note, such note has been fully paid with respect to such
shares), or were obtained by Optionee in the open public market, having a Fair
Market Value equal to the Exercise Price of the Shares being purchased; (iii)
by instructing the Company to withhold Shares otherwise issuable pursuant to
the exercise of the Option having a Fair Market Value equal to the Exercise
Price of the Shares being purchased (including the withheld Shares); (iv) by
waiver of compensation accrued by Optionee for services rendered; (v) by
delivery to the Company of a promissory note executed by Optionee which shall
include such terms and conditions as the Board shall approve in accordance with
the terms and conditions of the Plan; or (vi) a combination of the foregoing as
approved by the Board.

         (c) Withholding Taxes. Prior to the issuance of Shares upon exercise
of this Option, Optionee must pay, or make adequate provision for, any
applicable federal or state withholding obligations of the Company. Where
approved by the Board, Optionee may provide for payment of withholding taxes
upon exercise of the Option by requesting that the Company retain Shares with a
Fair Market Value equal to the minimum amount of taxes required to be withheld.
In such case, the Company shall issue the net number of Shares to Optionee by
deducting the Shares retained from the Shares exercised.

         (d) Issuance of Shares. Provided that such notice and payment are in
form and substance satisfactory to counsel for the Company, the Company shall
cause the Shares to be issued in the name of Optionee or Optionee's legal
representative.

     5.  NOTICE OF DISQUALIFYING DISPOSITION OF ISO SHARES. If this Option is
an ISO, and if Optionee sells or otherwise disposes of any of the Shares
acquired pursuant to the ISO on or before the later of: (a) the date two (2)
years after the Date of Grant, or (b) the date one (1) year after exercise of
the ISO, with respect to the Shares to be sold or disposed, Optionee shall
immediately notify the Company in writing of such sale or disposition. Optionee
acknowledges and agrees that Optionee may be subject to income tax withholding
by the Company on the compensation income recognized by Optionee from any such
early disposition by payment in cash or out of the current wages or earnings
payable to Optionee.

     6.  NONTRANSFERABILITY OF OPTION. This Option may not be transferred in
any manner, other than by will or by the laws of descent and distribution, and
may be exercised during Optionee's lifetime only by Optionee. The terms of this
Option shall be binding upon the executor, administrators, successors and
assigns of Optionee.

     7.  TAX CONSEQUENCES. OPTIONEE UNDERSTANDS THAT THE GRANT AND EXERCISE OF
THIS OPTION, AND THE SALE OF SHARES OBTAINED THROUGH THE EXERCISE OF THIS
OPTION, MAY HAVE TAX IMPLICATIONS THAT COULD RESULT IN ADVERSE TAX CONSEQUENCES
TO OPTIONEE. OPTIONEE REPRESENTS THAT OPTIONEE HAS CONSULTED WITH, OR WILL
CONSULT WITH, HIS OR HER TAX ADVISOR AND OPTIONEE FURTHER ACKNOWLEDGES THAT
OPTIONEE IS NOT RELYING OF THE COMPANY FOR ANY FINANCIAL, TAX OR OTHER ADVICE.

     8.  INTERPRETATION. Any dispute regarding the interpretation of this Stock
Option Grant Certificate shall be submitted by Optionee or the Company to the
Board, which shall review such dispute at its next regular meeting. The
resolution of such a dispute by the Board shall be final and binding on the
Company and Optionee.

     9.  ENTIRE AGREEMENT. The Plan and the Exercise Agreement are incorporated
herein by this reference. Optionee acknowledges and agrees that the granting of
this Option constitutes a full accord, satisfaction and release of all
obligations or commitments made to Optionee by the Company or any of its
officers, directors, shareholders or affiliates with respect to the issuance of
any securities, or rights to acquire securities, of the Company or any of its
affiliates. This Stock Option Grant Certificate, the Plan and the Exercise
Agreement constitute the entire agreement of the parties hereto, and supersede
all prior undertakings and agreements with respect to the subject matter
hereof.

     10. VESTING AND EXERCISE OF SHARES. Subject to the terms of the Plan, this
Option and the Exercise Agreement, the Shares issued pursuant to the exercise
of this Option shall be subject to the vesting restrictions selected on the
reverse side of this Stock Option Grant Certificate and defined below. For
purposes of this Section, "Continuous Service" means a period of continuous
performance of services by Optionee for the Company, a Parent, or a Subsidiary,
as determined by the Board.

<PAGE>   4

     Four Year Vesting: Optionee may exercise this Option with respect to the
percentage of Shares set forth below only after Optionee has completed the
following periods of Continuous Service following the date of grant:

         (a)  After twelve (12) months of Continuous Service, up to twenty-five
percent (25%) of the Shares;

         (b)  After thirteen (13) months of Continuous Service, and for each
additional month of Continuous Service thereafter through the end of the
forty-seventh (47th) month of Continuous Service, an additional two percent
(2%) of the Shares per month: and

         (c)  After forty-eight (48) months of Continuous Service, up to one
hundred percent (100%) of the Shares.

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