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                                                                    Exhibit 99.4



                          CORSAIR COMMUNICATIONS, INC.
                        1997 EMPLOYEE STOCK PURCHASE PLAN


I.      PURPOSE OF THE PLAN

        This Employee Stock Purchase Plan is intended to promote the interests
of Corsair Communications, Inc., a Delaware corporation, by providing eligible
employees with the opportunity to acquire a proprietary interest in the
Corporation through participation in a payroll-deduction based employee stock
purchase plan designed to qualify under Section 423 of the Code.

        Capitalized terms herein shall have the meanings assigned to such terms
in the attached Appendix.

II.     ADMINISTRATION OF THE PLAN

        The Plan Administrator shall have full authority to interpret and
construe any provision of the Plan and to adopt such rules and regulations for
administering the Plan as it may deem necessary in order to comply with the
requirements of Code Section 423. Decisions of the Plan Administrator shall be
final and binding on all parties having an interest in the Plan.

III.    STOCK SUBJECT TO PLAN

        A. The stock purchasable under the Plan shall be shares of authorized
but unissued or reacquired Common Stock, including shares of Common Stock
purchased on the open market. The maximum number of shares of Common Stock which
may be issued over the term of the Plan shall not exceed six hundred sixty-six
thousand six hundred sixty seven (666,667) shares. Such share reserve includes
an increase of 400,000 shares authorized by the Board on March 25, 1999, subject
to stockholder approval at the 1999 Annual Meeting.

        B. Should any change be made to the Common Stock by reason of any stock
split, stock dividend, recapitalization, combination of shares, exchange of
shares or other change affecting the outstanding Common Stock as a class without
the Corporation's receipt of consideration, appropriate adjustments shall be
made to (i) the maximum number and class of securities issuable under the Plan,
(ii) the maximum number and class of securities purchasable per Participant on
any one Purchase Date and (iii) the number and class of securities and the price
per share in effect under each outstanding purchase right in order to prevent
the dilution or enlargement of benefits thereunder.

IV.     OFFERING PERIODS



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        A. Shares of Common Stock shall be offered for purchase under the Plan
through a series of successive offering periods until such time as (i) the
maximum number of shares of Common Stock available for issuance under the Plan
shall have been purchased or (ii) the Plan shall have been sooner terminated.

        B. The initial offering period shall commence as of the Effective Time
of the Plan and shall continue until July 31, 1999. Thereafter, each successive
offering period shall be of 24 months duration. The next offering period shall
commence on the first business day in August 1999, and subsequent offering
periods shall commence as designated by the Plan Administrator. Notwithstanding
the above, the Plan Administrator may shorten the duration of any offering
period to less than twenty-four (24) months provided that such action is taken
prior to the start date of such offering period.

        C. Each offering period shall be comprised of a series of one or more
successive Purchase Intervals. Purchase Intervals shall run from the first
business day in February each year to the last business day in July of the same
year and from the first business day in August each year to the last business
day in January of the following year. Accordingly, the first Purchase Interval
in effect under the initial offering period shall commence at the Effective Time
and terminate on the last business day in January 1998.

        D. Should the Fair Market Value per share of Common Stock on any
Purchase Date within an offering period be less than the Fair Market Value per
share of Common Stock on the start date of that offering period, then that
offering period shall automatically terminate immediately after the purchase of
shares of Common Stock on such Purchase Date, and a new offering period shall
commence on the next business day following such Purchase Date. The new offering
period shall have a duration of twenty four (24) months, unless a shorter
duration is established by the Plan Administrator within five (5) business days
following the start date of that offering period.

V.      ELIGIBILITY

        A. Each individual who is an Eligible Employee on the start date of any
offering period under the Plan may enter that offering period on such start date
or on any subsequent Semi-Annual Entry Date within that offering period,
provided he or she remains an Eligible Employee.

        B. Each individual who first becomes an Eligible Employee after the
start date of an offering period may enter that offering period on any
subsequent Semi-Annual Entry Date within that offering period on which he or she
is an Eligible Employee.

        C. The date an individual enters an offering period shall be designated
his or her Entry Date for purposes of that offering period.

        D. To participate in the Plan for a particular offering period, the
Eligible Employee must complete the enrollment forms prescribed by the Plan
Administrator





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(including a stock purchase agreement and a payroll deduction authorization) and
file such forms with the Plan Administrator (or its designate) on or before his
or her scheduled Entry Date.

VI.     PAYROLL DEDUCTIONS

        A. The payroll deduction authorized by the Participant for purposes of
acquiring shares of Common Stock during an offering period may be any multiple
of one percent (1%) of the Base Salary paid to the Participant during each
Purchase Interval within that offering period, up to a maximum of ten percent
(10%). The deduction rate so authorized shall continue in effect throughout the
offering period, except to the extent such rate is changed in accordance with
the following guidelines:

               (i) The Participant may, at any time during the offering period,
        reduce his or her rate of payroll deduction to become effective as soon
        as possible after filing the appropriate form with the Plan
        Administrator. The Participant may not, however, effect more than one
        (1) such reduction per Purchase Interval.

               (ii) The Participant may, prior to the commencement of any new
        Purchase Interval within the offering period, increase the rate of his
        or her payroll deduction by filing the appropriate form with the Plan
        Administrator. The new rate (which may not exceed the ten percent (10%)
        maximum) shall become effective on the start date of the first Purchase
        Interval following the filing of such form.

        B. Payroll deductions shall begin on the first pay day following the
Participant's Entry Date into the offering period and shall (unless sooner
terminated by the Participant) continue through the pay day ending with or
immediately prior to the last day of that offering period. The amounts so
collected shall be credited to the Participant's book account under the Plan,
but no interest shall be paid on the balance from time to time outstanding in
such account. The amounts collected from the Participant shall not be held in
any segregated account or trust fund and may be commingled with the general
assets of the Corporation and used for general corporate purposes.

        C. Payroll deductions shall automatically cease upon the termination of
the Participant's purchase right in accordance with the provisions of the Plan.

        D. The Participant's acquisition of Common Stock under the Plan on any
Purchase Date shall neither limit nor require the Participant's acquisition of
Common Stock on any subsequent Purchase Date, whether within the same or a
different offering period.

VII.    PURCHASE RIGHTS

        A. GRANT OF PURCHASE RIGHT. A Participant shall be granted a separate
purchase right for each offering period in which he or she participates. The






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purchase right shall be granted on the Participant's Entry Date into the
offering period and shall provide the Participant with the right to purchase
shares of Common Stock, in a series of successive installments over the
remainder of such offering period, upon the terms set forth below. The
Participant shall execute a stock purchase agreement embodying such terms and
such other provisions (not inconsistent with the Plan) as the Plan Administrator
may deem advisable.

        Under no circumstances shall purchase rights be granted under the Plan
to any Eligible Employee if such individual would, immediately after the grant,
own (within the meaning of Code Section 424(d)) or hold outstanding options or
other rights to purchase, stock possessing five percent (5%) or more of the
total combined voting power or value of all classes of stock of the Corporation
or any Corporate Affiliate.

        B. EXERCISE OF THE PURCHASE RIGHT. Each purchase right shall be
automatically exercised in installments on each successive Purchase Date within
the offering period, and shares of Common Stock shall accordingly be purchased
on behalf of each Participant (other than Participants whose payroll deductions
have previously been refunded pursuant to the Termination of Purchase Right
provisions below) on each such Purchase Date. The purchase shall be effected by
applying the Participant's payroll deductions for the Purchase Interval ending
on such Purchase Date to the purchase of whole shares of Common Stock at the
purchase price in effect for the Participant for that Purchase Date.

        C. PURCHASE PRICE. The purchase price per share at which Common Stock
will be purchased on the Participant's behalf on each Purchase Date within the
offering period shall not be less than eighty-five percent (85%) of the lower of
(i) the Fair Market Value per share of Common Stock on the Participant's Entry
Date into that offering period or (ii) the Fair Market Value per share of Common
Stock on that Purchase Date.

        D. NUMBER OF PURCHASABLE SHARES. The number of shares of Common Stock
purchasable by a Participant on each Purchase Date during the offering period
shall be the number of whole shares obtained by dividing the amount collected
from the Participant through payroll deductions during the Purchase Interval
ending with that Purchase Date by the purchase price in effect for the
Participant for that Purchase Date but in no event may any Participant purchase
more than 7,500 shares on any Purchase Date.

        E. EXCESS PAYROLL DEDUCTIONS. Any payroll deductions not applied to the
purchase of shares of Common Stock on any Purchase Date because they are not
sufficient to purchase a whole share of Common Stock shall be held for the
purchase of Common Stock on the next Purchase Date. However, any payroll
deductions not applied to the purchase of Common Stock by reason of the
limitation on the maximum number of shares purchasable by the Participant on the
Purchase Date shall be promptly refunded.






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        F. TERMINATION OF PURCHASE RIGHT. The following provisions shall govern
the termination of outstanding purchase rights:

                      (i) A Participant may, at any time prior to the next
        scheduled Purchase Date in the offering period, terminate his or her
        outstanding purchase right by filing the appropriate form with the Plan
        Administrator (or its designate), and no further payroll deductions
        shall be collected from the Participant with respect to the terminated
        purchase right. Any payroll deductions collected during the Purchase
        Interval in which such termination occurs shall, at the Participant's
        election, be immediately refunded or held for the purchase of shares on
        the next Purchase Date. If no such election is made at the time such
        purchase right is terminated, then the payroll deductions collected with
        respect to the terminated right shall be refunded as soon as possible.

                      (ii) The termination of such purchase right shall be
        irrevocable, and the Participant may not subsequently rejoin the
        offering period for which the terminated purchase right was granted. In
        order to resume participation in any subsequent offering period, such
        individual must re-enroll in the Plan (by making a timely filing of the
        prescribed enrollment forms) on or before his or her scheduled Entry
        Date into that offering period.

                      (iii) Should the Participant cease to remain an Eligible
        Employee for any reason (including death, disability or change in
        status) while his or her purchase right remains outstanding, then that
        purchase right shall immediately terminate, and all of the Participant's
        payroll deductions for the Purchase Interval in which the purchase right
        so terminates shall be immediately refunded. However, should the
        Participant cease to remain in active service by reason of an approved
        unpaid leave of absence, then the Participant shall have the right,
        exercisable up until the last business day of the Purchase Interval in
        which such leave commences, to (a) withdraw all the payroll deductions
        collected to date on his or her behalf for that Purchase Interval or (b)
        have such funds held for the purchase of shares on his or her behalf on
        the next scheduled Purchase Date. In no event, however, shall any
        further payroll deductions be collected on the Participant's behalf
        during such leave. Upon the Participant's return to active service, his
        or her payroll deductions under the Plan shall automatically resume at
        the rate in effect at the time the leave began, unless the Participant
        withdraws from the Plan prior to his or her return.

        G. CORPORATE TRANSACTION. Each outstanding purchase right shall
automatically be exercised, immediately prior to the effective date of any
Corporate Transaction, by applying the payroll deductions of each Participant
for the Purchase Interval in which such Corporate Transaction occurs to the
purchase of whole shares of Common Stock at a purchase price per share not less
than eighty-five percent (85%) of the lower of (i) the Fair Market Value per
share of Common Stock on the Participant's Entry Date into the offering period
in which such Corporate Transaction occurs or (ii) the Fair Market Value per
share of Common Stock immediately prior to the effective date of






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such Corporate Transaction. However, the applicable limitation on the number of
shares of Common Stock purchasable per Participant shall continue to apply to
any such purchase.

        The Corporation shall use its best efforts to provide at least ten
(10)-days prior written notice of the occurrence of any Corporate Transaction,
and Participants shall, following the receipt of such notice, have the right to
terminate their outstanding purchase rights prior to the effective date of the
Corporate Transaction.

        H. PRORATION OF PURCHASE RIGHTS. Should the total number of shares of
Common Stock to be purchased pursuant to outstanding purchase rights on any
particular date exceed the number of shares then available for issuance under
the Plan, the Plan Administrator shall make a pro-rata allocation of the
available shares on a uniform and nondiscriminatory basis, and the payroll
deductions of each Participant, to the extent in excess of the aggregate
purchase price payable for the Common Stock pro-rated to such individual, shall
be refunded.

        I. ASSIGNABILITY. The purchase right shall be exercisable only by the
Participant and shall not be assignable or transferable by the Participant.

        J. STOCKHOLDER RIGHTS. A Participant shall have no stockholder rights
with respect to the shares subject to his or her outstanding purchase right
until the shares are purchased on the Participant's behalf in accordance with
the provisions of the Plan and the Participant has become a holder of record of
the purchased shares.

VIII.   ACCRUAL LIMITATIONS

        A. No Participant shall be entitled to accrue rights to acquire Common
Stock pursuant to any purchase right outstanding under this Plan if and to the
extent such accrual, when aggregated with (i) rights to purchase Common Stock
accrued under any other purchase right granted under this Plan and (ii) similar
rights accrued under other employee stock purchase plans (within the meaning of
Code Section 423) of the Corporation or any Corporate Affiliate, would otherwise
permit such Participant to purchase more than Twenty-Five Thousand Dollars
($25,000) worth of stock of the Corporation or any Corporate Affiliate
(determined on the basis of the Fair Market Value per share on the date or dates
such rights are granted) for each calendar year such rights are at any time
outstanding.

        B. For purposes of applying such accrual limitations to the purchase
rights granted under the Plan, the following provisions shall be in effect:

               (i) The right to acquire Common Stock under each outstanding
        purchase right shall accrue in a series of installments on each
        successive Purchase Date during the offering period on which such right
        remains outstanding.






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               (ii) No right to acquire Common Stock under any outstanding
        purchase right shall accrue to the extent the Participant has already
        accrued in the same calendar year the right to acquire Common Stock
        under one (1) or more other purchase rights at a rate equal to
        Twenty-Five Thousand Dollars ($25,000) worth of Common Stock (determined
        on the basis of the Fair Market Value per share on the date or dates of
        grant) for each calendar year such rights were at any time outstanding.

        C. If by reason of such accrual limitations, any purchase right of a
Participant does not accrue for a particular Purchase Interval, then the payroll
deductions which the Participant made during that Purchase Interval with respect
to such purchase right shall be promptly refunded.

        D. In the event there is any conflict between the provisions of this
Article and one or more provisions of the Plan or any instrument issued
thereunder, the provisions of this Article shall be controlling.

IX.     EFFECTIVE TIME AND TERM OF THE PLAN

        A. The Plan shall become effective at the Effective Time, provided no
purchase rights granted under the Plan shall be exercised, and no shares of
Common Stock shall be issued hereunder, until (i) the Plan shall have been
approved by the stockholders of the Corporation and (ii) the Corporation shall
have complied with all applicable requirements of the 1933 Act (including the
registration of the shares of Common Stock issuable under the Plan on a Form S-8
registration statement filed with the Securities and Exchange Commission), all
applicable listing requirements of any stock exchange (or the Nasdaq National
Market, if applicable) on which the Common Stock is listed for trading and all
other applicable requirements established by law or regulation. In the event
such stockholder approval is not obtained, or such compliance is not effected,
within twelve (12) months after the date on which the Plan is adopted by the
Board, the Plan shall terminate and have no further force or effect, and all
sums collected from Participants during the initial offering period hereunder
shall be refunded.

        B. Unless sooner terminated by the Board, the Plan shall terminate upon
the earliest of (i) the last business day in July 2007, (ii) the date on which
all shares available for issuance under the Plan shall have been sold pursuant
to purchase rights exercised under the Plan or (iii) the date on which all
purchase rights are exercised in connection with a Corporate Transaction. No
further purchase rights shall be granted or exercised, and no further payroll
deductions shall be collected, under the Plan following such termination.

X.      AMENDMENT OF THE PLAN

        The Board may alter, amend, suspend or discontinue the Plan at any time
to become effective immediately following the close of any Purchase Interval.
However, the Board may not, without the approval of the Corporation's
stockholders, (i) materially






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increase the number of shares of Common Stock issuable under the Plan or the
maximum number of shares purchasable per Participant on any one Purchase Date,
except for permissible adjustments in the event of certain changes in the
Corporation's capitalization, (ii) alter the purchase price formula so as to
reduce the purchase price payable for the shares of Common Stock purchasable
under the Plan or (iii) materially increase the benefits accruing to
Participants under the Plan or materially modify the requirements for
eligibility to participate in the Plan.

        On March 25, 1999, the Board amended the Plan to increase the maximum
number of shares of Common Stock authorized for issuance over the term of the
Plan from 266,667 shares to 666,667 shares. This amendment is subject to
stockholder approval at the 1999 Annual Meeting.

XI.     GENERAL PROVISIONS

        A. All costs and expenses incurred in the administration of the Plan
shall be paid by the Corporation.

        B. Nothing in the Plan shall confer upon the Participant any right to
continue in the employ of the Corporation or any Corporate Affiliate for any
period of specific duration or interfere with or otherwise restrict in any way
the rights of the Corporation (or any Corporate Affiliate employing such person)
or of the Participant, which rights are hereby expressly reserved by each, to
terminate such person's employment at any time for any reason, with or without
cause.

        C. The provisions of the Plan shall be governed by the laws of the State
of Delaware without resort to that State's conflict-of-laws rules.


























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                                   SCHEDULE A


                          CORPORATIONS PARTICIPATING IN
                          EMPLOYEE STOCK PURCHASE PLAN
                            AS OF THE EFFECTIVE TIME


                          Corsair Communications, Inc.



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                                    APPENDIX


        The following definitions shall be in effect under the Plan:

        A. BASE SALARY shall mean the (i) regular base salary paid to a
Participant by one or more Participating Companies during such individual's
period of participation in one or more offering periods under the Plan plus (ii)
any pre-tax contributions made by the Participant to any Code Section 401(k)
salary deferral plan or any Code Section 125 cafeteria benefit program now or
hereafter established by the Corporation or any Corporate Affiliate. The
following items of compensation shall NOT be included in Base Salary: (i) all
overtime payments, bonuses, commissions (other than those functioning as base
salary equivalents), profit-sharing distributions and other incentive-type
payments and (ii) any and all contributions (other than Code Section 401(k) or
Code Section 125 contributions) made on the Participant's behalf by the
Corporation or any Corporate Affiliate under any employee benefit or welfare
plan now or hereafter established.

        B. BOARD shall mean the Corporation's Board of Directors.

        C. CODE shall mean the Internal Revenue Code of 1986, as amended.

        D. COMMON STOCK shall mean the Corporation's common stock.

        E. CORPORATE AFFILIATE shall mean any parent or subsidiary corporation
of the Corporation (as determined in accordance with Code Section 424), whether
now existing or subsequently established.

        F. CORPORATE TRANSACTION shall mean either of the following
stockholder-approved transactions to which the Corporation is a party:

               (i) a merger or consolidation in which securities possessing more
        than fifty percent (50%) of the total combined voting power of the
        Corporation's outstanding securities are transferred to a person or
        persons different from the persons holding those securities immediately
        prior to such transaction, or

               (ii) the sale, transfer or other disposition of all or
        substantially all of the assets of the Corporation in complete
        liquidation or dissolution of the Corporation.

        G. CORPORATION shall mean Corsair Communications, Inc., a Delaware
corporation, and any corporate successor to all or substantially all of the
assets or voting stock of Corsair Communications, Inc. which shall by
appropriate action adopt the Plan.

        H. EFFECTIVE TIME shall mean the time at which the Underwriting
Agreement is executed and finally priced. Any Corporate Affiliate which becomes
a






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Participating Corporation after such Effective Time shall designate a subsequent
Effective Time with respect to its employee-Participants.

        I. ELIGIBLE EMPLOYEE shall mean any person who is employed by a
Participating Corporation on a basis under which he or she is regularly expected
to render more than twenty (20) hours of service per week for more than five (5)
months per calendar year for earnings considered wages under Code Section
3401(a).

        J. ENTRY DATE shall mean the date an Eligible Employee first commences
participation in the offering period in effect under the Plan. The earliest
Entry Date under the Plan shall be the Effective Time.

        K. FAIR MARKET VALUE per share of Common Stock on any relevant date
shall be determined in accordance with the following provisions:

               (i) If the Common Stock is at the time traded on the Nasdaq
        National Market, then the Fair Market Value shall be the closing selling
        price per share of Common Stock on the date in question, as such price
        is reported by the National Association of Securities Dealers on the
        Nasdaq National Market or any successor system. If there is no closing
        selling price for the Common Stock on the date in question, then the
        Fair Market Value shall be the closing selling price on the last
        preceding date for which such quotation exists.

               (ii) If the Common Stock is at the time listed on any Stock
        Exchange, then the Fair Market Value shall be the closing selling price
        per share of Common Stock on the date in question on the Stock Exchange
        determined by the Plan Administrator to be the primary market for the
        Common Stock, as such price is officially quoted in the composite tape
        of transactions on such exchange. If there is no closing selling price
        for the Common Stock on the date in question, then the Fair Market Value
        shall be the closing selling price on the last preceding date for which
        such quotation exists.

               (iii) For purposes of the initial offering period which begins at
        the Effective Time, the Fair Market Value shall be deemed to be equal to
        the price per share at which the Common Stock is sold in the initial
        public offering pursuant to the Underwriting Agreement.

        L.     1933 ACT shall mean the Securities Act of 1933, as amended.

        M. PARTICIPANT shall mean any Eligible Employee of a Participating
Corporation who is actively participating in the Plan.

        N. PARTICIPATING CORPORATION shall mean the Corporation and such
Corporate Affiliate or Affiliates as may be authorized from time to time by the
Board to extend the benefits of the Plan to their Eligible Employees. The
Participating Corporations in the Plan as of the Effective Time are listed in
attached Schedule A.





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        O. PLAN shall mean the Corporation's Employee Stock Purchase Plan, as
set forth in this document.

        P. PLAN ADMINISTRATOR shall mean the committee of two (2) or more Board
members appointed by the Board to administer the Plan.

        Q. PURCHASE DATE shall mean the last business day of each Purchase
Interval. The initial Purchase Date shall be the last business day in January
1998.

        R. PURCHASE INTERVAL shall mean each successive six (6)-month period
within the offering period at the end of which there shall be purchased shares
of Common Stock on behalf of each Participant.

        S. SEMI-ANNUAL ENTRY DATE shall mean the first business day in February
and August each year on which an Eligible Employee may first enter an offering
period.

        T. STOCK EXCHANGE shall mean either the American Stock Exchange or the
New York Stock Exchange.

        U. UNDERWRITING AGREEMENT shall mean the agreement between the
Corporation and the underwriter or underwriters managing the initial public
offering of the Common Stock.