<PAGE>

                                                                    EXHIBIT 10.8
                                                                    ------------


                       Supplementary Security Agreement
                    Security Interest in Goods and Chattels


                                                       November 27, 1998
                                                -------------------------------
                                                              DATE

To:  Fleet National Bank

Gentlemen:

     This is a supplement to our Inventory, Accounts Receivable and Intangibles
Security Agreement (the "Agreement") with you bearing the effective date of even
date herewith.  It is hereby incorporated into said Agreement, shall have a term
concurrent therewith and is a part thereof.

     1.  In addition to your other security, we hereby grant you a continuing
security interest in all machinery, equipment and other goods (as defined in
Article 9 of the Uniform Commercial Code) whether now owned or hereafter
acquired by us and wherever located, all replacements and substitutions therefor
or accessions thereto and all proceeds thereof (all herein referred to
collectively as "Collateral") and including, also without limitation, all
proceeds of fire or other insurance covering the aforesaid property.

     2.  The Collateral shall be security for all Obligations (as defined in the
Agreement).  Until all Obligations have been fully satisfied, your security
interest in the Collateral shall continue in full force and effect and you will
at all times after the occurrence of any Event of Default under the letter
agreement described below have the right to the physical possession of the
Collateral and to maintain such possession on our premises or to remove the
Collateral or any part thereof to such other places as you may desire.  If you
exercise your right to take possession of the Collateral, we shall, upon your
demand, assemble the Collateral and make it available to you at a place
reasonably convenient to you.  In addition, with respect to all Collateral, you
shall have all of the rights and remedies set forth in the Agreement and all of
the rights and remedies provided in the Uniform Commercial Code.

     3.  [Deleted]

     4.  We represent, warrant the covenant that (a) the Collateral is in our
possession at 500 Donald Lynch Boulevard, Marlborough, County of Middlesex,
Commonwealth of Massachusetts; (b) we are the lawful owners of the Collateral
and have the sole right and lawful authority to deliver this instrument; (c) the
Collateral and every part thereof is and will be free and clear of all security
interests, liens and encumbrances of every kind, nature and description except
as follows:  purchase money security interests and other exceptions permitted by
letter agreement of even date herewith between the Borrower and the Bank, and we
will warrant and defend the Collateral against the claims and demands of all
persons; (d) we will keep the Collateral free and clear of all attachments,
levies, taxes, liens, security interests and encumbrances of every kind and
nature, except as listed above, and we will at our own cost and expense, keep
the Collateral in a good state of repair and will
<PAGE>

                                                                    EXHIBIT 10.8
                                                                    ------------


not waste or destroy the same or any part thereof except for items disposed of
in the ordinary course to the extent expressly permitted by the aforesaid letter
agreement and will not be negligent in the care and use thereof; (e) we will not
without your prior written consent, sell, assign, mortgage, lease or otherwise
dispose of the Collateral except for obsolete or worn out items disposed of in
the ordinary course and except for liens permitted by the aforesaid letter
agreement; (f) we will insure the Collateral in your name against loss or damage
by fire, theft, burglary, pilferage, and such other hazards as you shall
specify, in amounts and under policies by insurers acceptable to you, and if we
fail to do so, you may procure such insurance and charge the cost to our loan
account; (g) as further assurance for the payment and performance of the
Obligations, we hereby assign to you all sums, including returned or unearned
premiums, which may become payable under any policy of insurance on the
Collateral and we hereby direct each insurance company issuing any such policy
to make payment of such sums directly to you; (h) except for items disposed of
in the ordinary course to the extent expressly permitted by the aforesaid letter
agreement we will not remove the Collateral from its present location without
your prior written consent and we will at all times, allow you or your
representatives free access to and right of inspection of the Collateral (see
attached Rider); (i) we will comply with the terms and conditions of any leases
covering the premises wherein the Collateral is located and any orders,
ordinances, laws or statutes of any city, state or other governmental department
having jurisdiction with respect to such premises or the conduct of business
thereon, and, when requested by you, we will execute any written instruments and
do any other acts necessary to effectuate more fully the purposes and provisions
of the Agreement; (j) we will indemnify and save you harmless from all loss,
cost, damage, liability or expenses including attorneys' fees that you may
sustain or incur by reason of defending or protecting your security interest or
the priority thereof or enforcing the Obligations, or in the prosecution or
defense of any action or proceeding concerning any matter growing out of or
connected with the Agreement, the Obligations or the Collateral (see attached
Rider).

     5.  You may, at your option, discharge any taxes, liens, security interests
or other encumbrances at any time levied or placed on the Collateral and not
permitted by the letter agreement and you may pay for the maintenance and
preservation of the Collateral and we will reimburse you on demand for any
payment made or any expense incurred by you  pursuant to the foregoing
authority, with interest at the rate provided in the Agreement.

                                Very truly yours,

Witnessed by:                   ASECO CORPORATION
                                -----------------------------------------------
                                               BORROWER
/s/ Sebastian J. Sicari
-------------------------
                                By: /s/Mary R. Barletta
                                    -------------------------------------------
                                Its: Chief Financial Officer

                                Accepted at Boston, Massachusetts  /s/ 11/30/98
                                                                   ------------
                                FLEET NATIONAL BANK

                                By: /s/Thomas W. Daires
                                   --------------------------------------------
                                Its:  Senior Vice President
<PAGE>

                                                                    EXHIBIT 10.8
                                                                    ------------


                   RIDER TO SUPPLEMENTARY SECURITY AGREEMENT
                 FROM ASECO CORPORATION TO FLEET NATIONAL BANK

     The foregoing Supplementary Security Agreement Agreement-Security Interest
in Goods and Chattels (the "Supplementary Security Agreement") is modified as
follows:

     1.   By inserting into Subsection 4(h) of the Supplementary Security
Agreement, immediately after the words "inspection of the Collateral", the
following:

          ", such access and right of inspection to be upon reasonable notice
          and during normal business hours, except that if an Event of Default
          under the aforesaid letter agreement has occurred and is continuing,
          the Bank may exercise such rights of access and inspection at any time
          and without any requirement for notice;"

     2.   By deleting the period at the end of Subsection 4(j) of the
Supplementary Security Agreement and by substituting in its stead the following:

          ", except for any such loss, cost, damage, liability or expenses
          arising out of the Bank's gross negligence or willful misconduct."