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                                                                    EXHIBIT 10.6


                    PATENT AND TRADEMARK SECURITY AGREEMENT

This PATENT AND TRADEMARK SECURITY AGREEMENT ("Agreement"), dated as of November
9, 1999, is entered into between PILOT NETWORK SERVICES, INC., a Delaware
corporation ("Grantor"), which has a mailing address at 1080 Marina Village
Parkway, Alameda, California 94501, and GREYROCK CAPITAL, a Division of Banc of
America Commerical Finance Corporation ("Greyrock"), which has a mailing address
at 10880 Wilshire Blvd., Suite 1850, Los Angeles, CA 90024.

                                   RECITALS

     A.  Grantor and Greyrock are, contemporaneously herewith, entering into
that certain Loan and Security Agreement ("Loan Agreement") and other
instruments, documents and agreements contemplated thereby or related thereto
(collectively, together with the Loan Agreement, the "Loan Documents"); and

     B.  Grantor is the owner of certain intellectual property, identified
below, in which Grantor is granting a security interest to Greyrock.

     NOW THEREFORE, in consideration of the mutual promises, covenants,
conditions, representations, and warranties hereinafter set forth and for other
good and valuable consideration, the parties hereto mutually agree as follows:

1.   DEFINITIONS AND CONSTRUCTION.

     1.1  Definitions. The following terms, as used in this Agreement, have the
following meanings:

          "Code" means the California Uniform Commercial Code, as amended and
           ----
supplemented from time to time, and any successor statute.

          "Collateral" means all of the following, whether now owned or
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hereafter acquired:

               (i)   Each of the trademarks and rights and interest which are
     capable of being protected as trademarks (including trademarks, service
     marks, designs, logos, indicia, tradenames, corporate names, company names,
     business names, fictitious business names, trade styles, and other source
     or business identifiers, and applications pertaining thereto), which are
     presently, or in the future may be, owned, created, acquired, or used
     (whether pursuant to a license or otherwise) by Grantor, in whole or in
     part, and all trademark rights with respect thereto throughout the world,
     including all proceeds thereof (including license royalties and proceeds of
     infringement suits), and rights to renew and extend such trademarks and
     trademark rights;

               (ii)  Each of the patents and patent applications which are
     presently, or

               in the future may be, owned, issued, acquired, or used (whether
     pursuant to a license or otherwise) by Grantor, in whole or in part, and
     all patent rights with respect thereto throughout the world, including all
     proceeds thereof (including license royalties and proceeds of infringement
     suits), foreign filing rights, and rights to extend such patents and patent
     rights;

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               (iii)   All of Grantor's right to the trademarks and trademark
     registrations listed on Exhibit A attached hereto, as the same may be
                             ---------
     updated hereafter from time to time;

               (iv)    All of Grantor's right, title, and interest, in and to
     the patents and patent applications listed on Exhibit B attached hereto, as
                                                   ---------
     the same may be updated hereafter from time to time;

               (v)     All of Grantor's right, title and interest to register
     trademark claims under any state or federal trademark law or regulation of
     any foreign country and to apply for, renew, and extend the trademark
     registrations and trademark rights, the right (without obligation) to sue
     or bring opposition or cancellation proceedings in the name of Grantor or
     in the name of Greyrock for past, present, and future infringements of the
     trademarks, registrations, or trademark rights and all rights (but not
     obligations) corresponding thereto in the United States and any foreign
     country;

               (vi)    All of Grantor's right, title, and interest in all
     patentable inventions, and to file applications for patent under federal
     patent law or regulation of any foreign country, and to request
     reexamination and/or reissue of the patents, the right (without obligation)
     to sue or bring interference proceedings in the name of Grantor or in the
     name of Greyrock for past, present, and future infringements of the
     patents, and all rights (but not obligations) corresponding thereto in the
     United States and any foreign country;

               (vii)   the entire goodwill of or associated with the businesses
     now or hereafter conducted by Grantor connected with and symbolized by any
     of the aforementioned properties and assets;

               (viii)  All general intangibles relating to the foregoing and
     all other intangible intellectual or other similar property of the Grantor
     of any kind or nature, associated with or arising out of any of the
     aforementioned properties and assets and not otherwise described above; and

               (ix)    All products and proceeds of any and all of the
     foregoing (including, without limitation, license royalties and proceeds of
     infringement suits) and, to the extent not otherwise included, all payments
     under insurance, or any indemnity, warranty, or guaranty payable by reason
     of loss or damage to or otherwise with respect to the Collateral.

         "Obligations" means all obligations, liabilities, and indebtedness of
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Grantor to Greyrock, whether direct, indirect, liquidated, or contingent, and
whether arising under this Agreement, the Loan Agreement, any other of the Loan
Documents, or otherwise, including all costs and expenses described in Section
9.8 hereof.

    1.2  Construction. Unless the context of this Agreement clearly requires
otherwise, references to the plural include the singular, references to the
singular include the plural, and the term "including" is not limiting. The words
"hereof," "herein," "hereby," "hereunder," and other similar terms refer to this
Agreement as a whole and not to any particular provision of this Agreement. Any
initially capitalized terms used but not defined herein shall have the meaning
set forth in the Loan Agreement. Any reference herein to any of the Loan
Documents includes any and all alterations, amendments, extensions,
modifications, renewals, or supplements thereto or thereof, as applicable.
Neither this Agreement nor any uncertainty or ambiguity herein shall be
construed or resolved against Greyrock or Grantor, whether under any rule of
construction or otherwise. On the contrary, this Agreement has been reviewed by
Grantor, Greyrock, and their respective counsel, and shall be construed and
interpreted according to the ordinary meaning of

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the words used so as to fairly accomplish the purposes and intentions of
Greyrock and Grantor. Headings have been set forth herein for convenience only,
and shall not be used in the construction of this Agreement.

2.   GRANT OF SECURITY INTEREST.

     To secure the complete and timely payment and performance of all
Obligations, and without limiting any other security interest Grantor has
granted to Greyrock, Grantor hereby grants, assigns, and conveys to Greyrock a
security interest in Grantor's entire right, title, an interest in and to the
Collateral.

3.   REPRESENTATIONS, WARRANTIES AND COVENANTS.

     Grantor hereby represents, warrants, and covenants that:

     3.1  Trademarks; Patents. A true and complete schedule setting forth all
federal and state trademark registrations owned or controlled by Grantor or
licensed to Grantor, together with a summary description and full information in
respect of the filing or issuance thereof and expiration dates is set forth on
Exhibit A; and a true and complete schedule setting forth all patent and patent
---------
applications owned or controlled by Grantor or licensed to Grantor, together
with a summary description and full information in respect of the filing or
issuance thereof and expiration dates is set forth Exhibit B.
                                                   ---------

     3.2  Validity; Enforceability. Each of the patents and trademarks is valid
and enforceable, and, except as disclosed to Greyrock, Grantor is not presently
aware of any past, present, or prospective claim by and third party that any of
the patents or trademarks are invalid or unenforceable, or to the best of
Grantor's knowledge that the use of any patents or trademarks violates the
rights of any third person, or of any basis for any such claims.

     3.3  Title. Grantor is the sole and exclusive owner of the entire and
unencumbered right, title, and interest in and to each of the patents, patent
applications, trademarks, and trademark registrations, free and clear of any
liens, charges, and encumbrances, including pledges, assignments, licenses, shop
rights, and covenants by Grantor not to sue third persons, other than Permitted
Liens.

     3.4  Notice. Grantor has used and will continue to use proper statutory
notice in connection with its use of each of the patents and trademarks.

     3.5  Quality. Grantor has used and will continue to use consistent
standards of high quality (which may be consistent with Grantor's past practices
or industry standard) in the manufacture, sale, and delivery of products and
services sold or delivered under or in connection with the trademarks,
including, to the extent applicable, in the operation and maintenance of its
merchandising operations, and will continue to maintain the validity of all
trademarks that are in Grantor's reasonable business judgement necessary for the
continuance of its business as then conducted.

     3.6  Perfection of Security Interest. Except for the filing of financing
statements in the appropriate governmental offices and filings with the United
States Patent and Trademark Office necessary to perfect the security interests
created hereunder, no authorization, approval, or other action by, and no notice
to or filing with, any governmental authority or regulatory body is required
either for the grant by Grantor of the security interest hereunder or for the
execution, delivery, or performance of this Agreement by Grantor or for the
perfection of or the exercise by Greyrock of its rights hereunder to the
Collateral in the United States.

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4.   AFTER-ACQUIRED PATENT OR TRADEMARK RIGHTS.

     If Grantor shall obtain rights to any new trademarks, any new patentable
inventions or become entitled to the benefit of any patent application or patent
for any reissue, division, or continuation, of any patent, the provisions of
this Agreement shall automatically apply thereto.  Grantor shall give prompt
notice in writing to Greyrock with respect to any such new trademarks or
patents, or renewal or extension of any trademark registration.  Grantor shall
bear any expenses incurred in connection with future patent applications or
trademark registrations.  Without limiting Grantor's obligation under this
Section 4, Grantor authorizes Greyrock to modify this Agreement by amending
Exhibits A or B to include any such new patent or trademark rights.
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Notwithstanding the foregoing, no failure to so modify this Agreement or amend
Exhibits A or B shall in any way affect, invalidate or detract from Greyrock's
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continuing security interest in all Collateral, whether or not listed on Exhibit
                                                                         -------
A or B.
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5.   LITIGATION AND PROCEEDINGS.

     Grantor shall commence and diligently prosecute in its own name, as the
real party in interest, for its own benefit, and its own expense, such suits,
administrative proceedings, or other action for infringement or other damages as
are in its reasonable business judgment necessary to protect the Collateral.
Grantor shall provide to Greyrock any information with respect thereto requested
by Greyrock. Greyrock shall provide at Grantor's expense all necessary
cooperation in connection with any such suits, proceedings, or action,
including, without limitation, joining as a necessary party. Following Grantor's
becoming aware thereof, Grantor shall notify Greyrock of the institution of, or
any adverse determination in, any proceeding in the United States Patent and
Trademark Office, or any United States, state, or foreign court regarding
Grantor's claim of ownership in any of the patents or trademarks, its right to
apply for the same, or its right to keep and maintain such patent or trademark
rights.

6.   POWER OF ATTORNEY

     Grantor hereby appoints Greyrock as Grantor's true and lawful attorney,
with full power of substitution, to do any or all of the following, in the name,
place and stead of Grantor: (a) file this Agreement (or an abstract hereof) or
any other document describing Greyrock's interest in the Collateral with the
United States Patent and Trademark Office; (b) execute any modification of this
Agreement pursuant to Section 4 of this Agreement; (c) take any action and
execute any instrument which Greyrock may, in its reasonable discretion, deem
necessary or advisable to accomplish the purposes of this Agreement; and (d)
following an Event of Default (as defined in the Loan Agreement) that results in
the acceleration of the Obligations, (i) endorse Grantor's name on all
applications, documents, papers and instruments necessary for Greyrock to use or
maintain the Collateral; (ii) ask, demand, collect, sue for, recover, impound,
receive, and give acquittance and receipts for money due or to become due under
or in respect of any of the Collateral; (iii) file any claims or take any action
or institute any proceedings that Greyrock may deem necessary or desirable for
the collection of any of the Collateral or otherwise enforce Greyrock's rights
with respect to any of the Collateral, and (iv) assign, pledge, convey, or
otherwise transfer title in or dispose of the Collateral to any person.

7.   RIGHT TO INSPECT.

     Grantor grants to Greyrock and its employees and agents the right to visit
Grantor's plants and facilities which manufacture, inspect, or store products
sold under any of the patents or trademarks, and to inspect the products and
quality control records relating thereto at reasonable times during regular
business hours in accordance with the Loan Agreement.

8.   SPECIFIC REMEDIES.

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     Upon the occurrence of any Event of Default (as defined in the Loan
Agreement) that results in the acceleration of the Obligations, Greyrock shall
have, in addition to, other rights given by law or in this Agreement, the Loan
Agreement, or in any other Loan Document, all of the rights and remedies with
respect to the Collateral of a secured party under the Code, including the
following:

     8.1       Notification. Greyrock may notify licensees to make royalty
payments on license agreements directly to Greyrock;

     8.2       Sale. Greyrock may sell or assign the Collateral and associated
goodwill at public or private sale for such amounts, and at such time or times
as Greyrock deems advisable. Any requirement of reasonable notice of any
disposition of the Collateral shall be satisfied if such notice is sent to
Grantor seven (7) days prior to such disposition. Grantor shall be credited with
the net proceeds of such sale only when they are actually received by Greyrock,
and Grantor shall continue to be liable for any deficiency remaining after the
Collateral is sold or collected. If the sale is to be a public sale, Greyrock
shall also give notice of the time and place by publishing a notice one time at
least seven (7) days before the date of the sale in a newspaper of general
circulation in the county in which the sale is to be held. To the maximum extent
permitted by applicable law, Greyrock may be the purchaser of any or all of the
Collateral and associated goodwill at any public sale and shall be entitled, for
the purpose of bidding and making settlement or payment of the purchase price
for all or any portion of the Collateral sold at any public sale, to use and
apply all or any part of the Obligations as a credit on account of the purchase
price of any Collateral payable by Greyrock at such sale.

9.   GENERAL PROVISIONS.

     9.1       Effectiveness. This Agreement shall be binding and deemed
effective when executed by Grantor and Greyrock.

     9.2       Notices. Except to the extent otherwise provided herein, all
notices, demands, and requests that either party is required or elects to give
to the other shall be in writing and shall be governed by the notice provisions
of the Loan Agreement.

     9.3       No Waiver. No course of dealing between Grantor and Greyrock, nor
any failure to exercise nor any delay in exercising, on the part of Greyrock,
any right, power, or privilege under this Agreement or under the Loan Agreement
or any other agreement, shall operate as a waiver. No single or partial exercise
of any right, power, or privilege under this Agreement or under the Loan
Agreement or any other agreement by Greyrock shall preclude any other or further
exercise of such right, power, or privilege or the exercise of any other right,
power, or privilege by Greyrock.

     9.4       Rights Are Cumulative. All of Greyrock's rights and remedies with
respect to the Collateral whether established by this Agreement, the Loan
Agreement, or any other documents or agreements, or by law shall be cumulative
and may be exercised concurrently or in any other.

     9.5       Successors. The benefits and burdens of this Agreement shall
inure to the benefit of and be binding upon the respective successors and
permitted assigns of the parties; provided that Grantor may not transfer any of
the Collateral or any rights hereunder, without the prior written consent of
Greyrock, except as specifically permitted hereby.

     9.6       Severability. The provisions of this Agreement are severable. If
any provision of this Agreement is held invalid or unenforceable in whole or in
part in any jurisdiction, then such invalidity or unenforceability shall affect
only such provision, or part thereof, in such

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jurisdiction, and shall not in any manner affect such provision or part thereof
in any other jurisdiction, or any other provision of this Agreement in any
jurisdiction.

     9.7       Entire Agreement. This Agreement is subject to modification only
by a writing signed by the parties, except as provided in Section 4 of this
Agreement. To the extent that any provision of this Agreement conflicts with any
provision of the Loan Agreement, the provision giving Greyrock greater rights or
remedies shall govern, it being understood that the purpose of this Agreement is
to add to, and not detract from, the rights granted to Greyrock under the Loan
Agreement. This Agreement, the Loan Agreement, and the documents relating
thereto comprise the entire agreement of the parties with respect to the matters
addressed in this Agreement.

     9.8       Fees and Expenses. Grantor shall pay to Greyrock on demand all
reasonable costs and expenses that Greyrock pays or incurs in connection with
the negotiation, preparation, consummation, administration, enforcement, and
termination of this Agreement, including: (a) reasonable attorneys' and
paralegals' fees and disbursements of counsel to Greyrock; (b) reasonable costs
and expenses (including reasonable attorneys' and paralegals' fees and
disbursements) for any amendment, supplement, waiver, consent, or subsequent
closing in connection with this Agreement and the transactions contemplated
hereby; (c) reasonable costs and expenses of lien and title searches; (d) taxes,
fees, and other charges for filing this Agreement at the United States Patent
and Trademark Office, or for filing financing statements, and continuations, and
other actions to perfect, protect, and continue the security interest created
hereunder; (e) reasonable sums paid or incurred to pay any amount or take any
action required of Grantor under this Agreement that Grantor fails to pay or
take; (f) reasonable costs and expenses of preserving and protecting the
Collateral; and (g) reasonable costs and expenses (including reasonable
attorneys' and paralegals' fees and disbursements) paid or incurred to enforce
the security interest created hereunder, sell or otherwise realize upon the
Collateral, and otherwise enforce the provisions of this Agreement, or to defend
any claims made or threatened against the Greyrock arising out of the
transactions contemplated hereby (including preparations for the consultations
concerning any such matters). The foregoing shall not be construed to limit any
other provisions of this Agreement or the Loan Documents regarding costs and
expenses to be paid by Grantor. The parties agree that reasonable attorneys' and
paralegals' fees and costs incurred in enforcing any judgment are recoverable as
a separate item in addition to fees and costs incurred in obtaining the judgment
and that the recovery of such attorneys' and paralegals' fees and costs is
intended to survive any judgment, and is not to be deemed merged into any
judgment.

     9.9       Indemnity. Grantor shall protect, defend, indemnify, and hold
harmless Greyrock and Greyrock's assigns from all liabilities, losses, and costs
(including without limitation reasonable attorneys' fees) incurred or imposed on
Greyrock relating to the matters in this Agreement.

     9.10      Further Assurances. At Greyrock's reasonable request, Grantor
shall execute and deliver to Greyrock any further instruments or documentation,
and perform any acts, that may be reasonably necessary or appropriate to
implement this Agreement, the Loan Agreement or any other agreement, and the
documents relating thereto, including without limitation any instrument or
documentation reasonably necessary or appropriate to create, maintain, perfect,
or effectuate Greyrock's security interests in the Collateral.

     9.11      Release. At such time as Grantor shall completely satisfy all of
the Obligations and the Loan Agreement shall be terminated, Greyrock shall
promptly execute and deliver to Grantor all assignments and other instruments as
may be reasonably necessary or proper to terminate Greyrock's security interest
in the Collateral, subject to any disposition of the Collateral which may have
been made by Greyrock pursuant to this Agreement. For the purpose of this
Agreement, the Obligations shall be deemed to continue if Grantor enters into
any

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bankruptcy or similar proceeding at a time when any amount paid to Greyrock
could be ordered to be repaid as a preference or pursuant to a similar theory,
and shall continue until it is finally determined that no such repayment can be
ordered.

     9.12      Governing Law. The validity and interpretation of this Agreement
and the rights and obligations of the parties shall be governed by the laws of
the State of California, excluding its conflict of law rules to the extent such
rules would apply the law of another jurisdiction, and the United States. The
parties agree that all actions or proceedings arising in connection with this
Agreement shall be tried and litigated only in the state and federal courts
located in the County of Los Angeles, State of California or, at the sole option
of Greyrock, in any other court in which Greyrock shall initiate legal or
equitable proceedings and which has subject matter jurisdiction over the matter
in controversy. Each of Grantor and Greyrock waives, to the extent permitted
under applicable law, any right they may have to assert the doctrine of forum
non conveniens or to object to venue to the extent any proceeding is brought in
accordance with this Section.

     9.13      Waiver of Right to Jury Trial. GREYROCK AND GRANTOR EACH HEREBY
WAIVE THE RIGHT TO TRIAL BY JURY IN ANY ACTION OR PROCEEDING BASED UPON, ARISING
OUT OF, OR IN ANY WAY RELATING TO: (I) THIS AGREEMENT; OR (II) ANY OTHER PRESENT
OR FUTURE INSTRUMENT OR AGREEMENT BETWEEN GREYROCK AND GRANTOR; OR (III) ANY
CONDUCT, ACTS OR OMISSIONS OF GREYROCK OR GRANTOR OR ANY OF THEIR DIRECTORS,
OFFICERS, EMPLOYEES, AGENTS, ATTORNEYS OR ANY OTHER PERSONS AFFILIATED WITH
GREYROCK OR GRANTOR; IN EACH OF THE FOREGOING CASES, WHETHER SOUNDING IN
CONTRACT OR TORT OR OTHERWISE.

     IN WITNESS WHEREOF, the parties have executed this Agreement on the date
first written above.

GREYROCK CAPITAL, a Division of Banc         PILOT NETWORK SERVICES, INC.
of America Commercial Finance Corporation


By /s/ Lisa Nagano
   --------------------------------------
Title Senior Vice President                  By /s/ William C. Leetham
      -----------------------------------       -------------------------------
                                             Title Chief Financial Officer
                                                   ----------------------------

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