EXHIBIT 10.4




July 30, 2004


Sand Hill IT Security Acquisition Corp.
3000 Sand Hill Road
Building 1, Suite 240
Menlo Park, CA  94025

Newbridge Securities Corporation
I-Bankers Securities, Incorporated
c/o Newbridge Securities Corporation
1451 West Cypress Creek Road
Fort Lauderdale, FL  33309


Re:  Initial Public Offering


Gentlemen:

     The undersigned stockholder,  officer and director of Sand Hill IT Security
Acquisition  Corp. (the "Company"),  in  consideration  of Newbridge  Securities
Corporation  and  I-Bankers  Securities   Incorporated  (the  "Representatives")
entering  into a letter of intent (the  "Letter of Intent") to  underwrite  (the
"Representatives")  an initial public  offering of the securities of the Company
("IPO") and  embarking on the IPO  process,  hereby  agrees as follows  (certain
capitalized terms used herein are defined in paragraph 12 hereof):

     1. If the  Company  solicits  approval  of its  stockholders  of a Business
Combination,  the  undersigned  will  vote all  Insider  Shares  owned by him in
accordance with the majority of the votes cast by the holders of the IPO Shares.

     2. In the event that the Company fails to consummate a Business Combination
within  18  months  from  the  effective  date  (the  "Effective  Date")  of the
registration statement relating to the IPO (or 24 months under the circumstances
described in the prospectus  relating to the IPO), the undersigned will take all
reasonable actions within his power to cause the Company to liquidate as soon as
reasonably practicable. The undersigned waives any and all rights he may have to
receive any  distribution of cash,  property or other assets as a result of such
liquidation with respect to his Insider Shares.

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     3. In order to minimize  potential  conflicts  of interest  which may arise
from multiple affiliations, the undersigned agrees to present to the Company for
its  consideration,  prior to  presentation  to any other person or entity,  any
suitable opportunity to acquire an operating business,  until the earlier of the
consummation  by the Company of a Business  Combination,  the liquidation of the
Company  or until  such  time as the  undersigned  ceases  to be an  officer  or
director of the Company,  subject to any pre-existing  fiduciary obligations the
undersigned might have.

     4. The  undersigned  acknowledges  and  agrees  that the  Company  will not
consummate any Business  Combination that involves a company which is affiliated
with  any of the  Insiders  unless  the  Company  obtains  an  opinion  from  an
independent investment banking firm reasonably acceptable to the Representatives
that the  business  combination  is fair to the  Company's  stockholders  from a
financial perspective.

     5. Neither the  undersigned,  any member of the family of the  undersigned,
nor any  Affiliate of the  undersigned  will be entitled to receive and will not
accept any  compensation  for  services  rendered  to the  Company  prior to the
consummation  of the Business  Combination;  provided  that,  commencing  on the
Effective Date, Sand Hill Security,  LLC, a limited  liability company ("Related
Party"),  shall be allowed to charge the Company an  allocable  share of Related
Party's overhead, up to $7,500 per month, to compensate it for the Company's use
of Related  Party's  offices,  utilities  and  personnel.  Related Party and the
undersigned  shall also be entitled to reimbursement  from the Company for their
out-of-pocket  expenses  incurred in connection with seeking and  consummating a
Business Combination.

     6. Neither the  undersigned,  any member of the family of the  undersigned,
nor any  Affiliate  of the  undersigned  will be entitled to receive or accept a
finder's fee or any other compensation in the event the undersigned,  any member
of the family of the undersigned or any Affiliate of the undersigned  originates
a Business Combination.

     7. The undersigned will escrow his Insider Shares for the three year period
commencing  on the  Effective  Date  subject  to the  terms  of a  Stock  Escrow
Agreement  which the Company will enter into with the  undersigned  and American
Stock Transfer & Trust Company as escrow agent.

     8. The undersigned agrees that, during the three year period terminating on
July 26, 2007, he will not become involved (whether as owner, manager, operator,
creditor,  partner,  shareholder,  joint venturer,  member,  employee,  officer,
director,  consultant or  otherwise)  with any  Acquisition  Fund (as defined in
Section 12(v) below),  unless such Acquisition Fund engages the  Representatives
to  be  the  managing  underwriters  of  the  initial  public  offering  of  the
Acquisition Fund's securities.

     The undersigned hereby agrees and acknowledges that (i) the Representatives
would be irreparably  injured in the event of a breach by the undersigned of any

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<PAGE>

of his obligations under this paragraph 8, (ii) monetary damages would not be an
adequate  remedy for any such  breach,  and (iii) the  Representatives  shall be
entitled to injunctive relief, in addition to any other remedy they may have, in
the event of such breach.

     9. I agree to serve as the  President  and a director of the Company  until
the earlier of the consummation by the Company of a Business  Combination or the
liquidation of the Company. The undersigned's biographical information furnished
to  the  Company  and  the  Representatives  included  in the  S-1  Registration
Statement  is true and  accurate  in all  respects,  does not omit any  material
information with respect to the undersigned's background and contains all of the
information  required to be disclosed pursuant to Section 401 of Regulation S-K,
promulgated  under the  Securities  Act of 1933, as amended.  The  undersigned's
Questionnaire  furnished to the Company and the  Representatives  and annexed as
Exhibit  A  hereto  is  true  and  accurate  in all  respects.  The  undersigned
represents and warrants that:

          (a) he is not subject to or a respondent  in any legal action for, any
     injunction,  cease-and-desist  order or order or  stipulation  to desist or
     refrain from any act or practice  relating to the offering of securities in
     any jurisdiction;

          (b) he has never been  convicted of or pleaded guilty to any crime (i)
     involving  any  fraud or (ii)  relating  to any  financial  transaction  or
     handling of funds of another person, or (iii) pertaining to any dealings in
     any  securities  and he is not  currently a defendant in any such  criminal
     proceeding; and

          (c) he has never been  suspended or expelled  from  membership  in any
     securities or  commodities  exchange or  association or had a securities or
     commodities license or registration denied, suspended or revoked.

     10. I have full right and power, without violating any agreement by which I
am bound, to enter into this letter  agreement and to serve as an officer of the
Company.

     11. I authorize any employer,  financial  institution,  or consumer  credit
reporting  agency to release to the  Representatives  and their respective legal
representatives  or agents (including any investigative  search firm retained by
the  Representatives)  any  information  they may have about my  background  and
finances (the  "Information").  Neither the Representatives nor their respective
agents shall be violating  my right of privacy in any manner in  requesting  and
obtaining  the  Information  and I hereby  release them from  liability  for any
damage whatsoever in that connection.

     12. As used herein,

          (i)  "Business  Combination"  shall  mean an  acquisition  by  merger,
     capital  stock  exchange,  asset or stock  acquisition,  reorganization  or
     otherwise, of an operating business selected by the Company;

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<PAGE>

          (ii) "Insiders" shall mean all officers, directors and stockholders of
     the Company immediately prior to the IPO;

          (iii) "Insider Shares" shall mean all of the shares of Common Stock of
     the Company owned by an Insider prior to the IPO;

          (iv) "IPO Shares"  shall mean the shares of Common Stock issued in the
     Company's IPO; and

          (v)  "Acquisition  Fund" shall mean any company formed with the intent
     to offer securities to the public and use the proceeds to consummate one or
     more  Business  Combinations  which  are  unspecified  at the  time  of the
     securities offering.



                                          /s/ Keith Walz
                                          -----------------------------------
                                          Keith Walz




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