Exhibit 10.5

                           
                           AMENDMENT NO. 4 TO LEASE

1.   Parties.
     ------- 

     This Amendment, dated as of September 30, 1993, is between North Andover
Mills Realty ("Landlord") and FTP Software, Inc. ("Tenant").

2.   Recitals.
     -------- 

     2.1  Landlord and Tenant have entered into a Lease, dated November 19,
1991, as amended, for space at North Andover Mills in North Andover,
Massachusetts (the "Lease"). Unless otherwise defined, terms used in this
Amendment have the same meanings as those used in the Lease.

     2.2  Tenant wants to lease the following additional space in the Project
(collectively, the "Additional Space"):  the top floor of Building 9, the top
floor of Building 9A, the space that is currently vacant on the second (2nd) and
third (3rd) floors of Building 44E, and the entire first (1st) floor of
Buildings 44E and 44W (all subject to Landlord's reservation of common areas as
shown).  The Additional Space is depicted in Exhibit "A" attached hereto and
incorporated herein by this reference, and is agreed to contain 19,415 square
feet of rentable area.  To accomplish this and other matters, for Ten and No/100
Dollars ($10.00) and other good and valuable consideration, the receipt and
sufficiency of which is acknowledged, the parties agree and the Lease is amended
as follows, notwithstanding anything to the contrary:

3.   Amendments.
     ---------- 

     3.1  In Section 1.1(c), the Premises now includes the Additional Space, and
therefore the agreed rentable area of the Premises is increased from 106,851
square feet to 126,266 square feet.

     3.2  Landlord grants to Tenant an option (the "Termination Option") to
terminate the Lease term only with respect to the Additional Space at the end of
the fifth (5th) calendar year after the "Additional Space Rental Start Date" (as
defined in Section 3.3 below).  There will be no further right to terminate.
The Termination Option can be exercised only by Tenant delivering unconditional
written notice of exercise to Landlord before the end of the fourth (4th)
calendar year after the Additional Space Rental Start Date.  If for any reason
Landlord does not actually receive this notice of exercise when required, the
termination Option will lapse and become null and void and there will be no
further right to terminate the Lease term. The Termination Option is granted to
and may be exercised by Tenant on the express condition that, at the time of the
exercise and at all times before the end of the fifth (5th) calendar year after
the Additional Space Rental Start Date, Tenant is not in default (and has not
committed acts or omission which would constitute a default with the passage of
time or

 
the giving of notice or both).  TIME IS ABSOLUTELY OF THE ESSENCE.  The
Termination Option is personal to the Tenant originally named in this Lease, and
it may not be exercised by or for anyone else.  If during the initial term
Tenant Transfers any part of this Lease or the Premises (except for permitted
subleases aggregating less than 16,000 square feet of rentable area), at
Landlord's written election this Termination Option will lapse and become null
and void, whether or not it has been exercised.

     3.3  In Section 1.1(f), Tenant's Percentage will be increased from 19.52%
to 20.22% on December 6, 1993 (the "Additional Space Rental Start Date").

     3.4  Base rent for the Premises allocable to the Additional Space will be
entirely abated until the Additional Space Rental Start Date.  Notwithstanding
anything to the contrary, starting as of the Additional Space Rental Start Date,
the annual base rent per square foot of rentable area in the Additional Space
will be as follows:

     (a)  $10.75 per square foot for the first five (5) years after the
Additional Space Rental Start Date.

     (b)  $9.00 per square foot for the remainder of the initial Lease term.

     (c)  For each Lease Year of the Option term:




                                   Annual Base Rent Per Rentable
                                   -----------------------------
                  Lease Year       Square Foot in Additional Space
                  ----------       -------------------------------
                                
                      11                       $10.13
                      12                        10.13
                      13                        11.55
                      14                        11.55
                      15                        11.55
 
                        
     3.5  Tenant will be solely responsible, at its expense, for providing all
necessary work and services to construct all necessary improvements to or that
are necessary in connection with the Additional Space (including, without
limitation, the Base Building Improvements described in Exhibit "B" attached
hereto and incorporated herein by this reference) to the equivalent fit, finish
and specifications as the rest of the Premises.  All work will be done
diligently and in a good and workmanlike manner, using new materials and in
compliance with all applicable Laws and the terms of this Lease.  Tenant's work
will include, without limitation, all necessary hookups, connections and tie-
ins, all necessary drawings, plans and engineering, and securing all necessary
permits, inspections, approvals and a final Certificate of Occupancy from the
Town of North Andover.  Tenant's work and the plans and specifications therefor
will be subject to the prior review and approval of and coordination and
supervision by Landlord or its representatives and will be performed so as not
to damage the

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rest of the Project or its Systems and Equipment.  In particular, Landlord will
have the right and be granted the opportunity to fully participate in the entire
bidding and acceptance process (including any re-bidding, as deemed necessary by
Landlord) with respect to the Base Building Improvements, and all contracts in
connection with the Base Building Improvements and the prices therefor must
first be approved by Landlord in writing.

     3.6  Landlord will reimburse to Tenant:  (a) a construction allowance of up
to Fifteen and 75/100 Dollars ($15.75) per square foot of rentable area in the
Additional Space to reimburse Tenant for all costs incurred and paid for by
Tenant directly related to the construction of the Additional Space (excluding
the Base Building Improvements); and (b) a construction allowance up to the
[___] amounts agreed to by Landlord as described in Section 3.5 above to
reimburse Tenant for all costs incurred and paid for by Tenant directly related
to the Base Building Improvements.  Tenant will submit paid invoices against
work in place for all reimbursements requested, and the reimbursements will be
paid within 30 days after the following conditions have been satisfied, and
provided that Tenant is not in default under the Lease:  (x) Tenant's work has
been fully paid for and completed in accordance with the plans therefor and the
terms of this Lease and Tenant and its architect (or other representative) and
contractors, so certify to Landlord; (y) Tenant delivers final and unconditional
lien releases from all contractors, subcontractors, laborers and suppliers and
certifies that all liens that have been or could be filed have been discharged
of record or waived, and the lien filing periods have run; and (z) Tenant
delivers to Landlord the final Certificate of Occupancy from the Town of North
Andover and a set of "as built" plans and drawings for the Additional Space.
Tenant will account separately for the costs incurred in Subsections (a) and (b)
above.  If Landlord does not reimburse the construction allowances to Tenant
when required, from and after the date that reimbursement was required the
unpaid portion of the construction allowance that is then due will bear interest
until paid at a rate per annum equal to the Wells Fargo Bank prime rate of
interest from time to time plus 3%.

     3.7  Article 28 of the Lease is deleted, and the following is substituted:

          "28.  EXPANSION OPTION.
                ---------------- 

                28.1   Landlord grants to Tenant one (1) option (the "Expansion
Option") to lease the Expansion Space on the same terms and conditions as this
Lease with respect to the Additional Space (including tenant improvement
allowance and Base Building Improvements), except as set forth below.
"Expansion Space" means the remainder of the space in Buildings 9 and 9A and all
of Building 22, all as so designated in Exhibit "A."  The Expansion Option can
be exercised only by Tenant delivering unconditional written notice of exercise
to Landlord at least six (6) months before the end of the first calendar year
after the Additional Space Rental Start Date.  If for any reason Landlord does
not actually receive this unconditional written notice of exercise when
required, the Expansion Option will lapse and become null and void.  The
Expansion Option is granted to and may be exercised by Tenant on the express
condition that, at the time of the exercise and at all times before vacant

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possession of the Expansion Space is delivered to Tenant, Tenant is not in
default.  TIME IS ABSOLUTELY OF THE ESSENCE.  The Expansion Option is personal
to the Tenant originally named in this Lease and may not be exercised by or for
anyone else, and if Tenant Transfers any part of this Lease or the Premises
(except for permitted subleases aggregating less than 16,000 square feet of
rentable area) before the beginning of the Expansion Option term, at Landlord's
election the Expansion Option will lapse and become null and void.

                28.2   Size of Expansion Space.  The parties agree that the
                       -----------------------                             
Expansion Space in Buildings 9 and 9A contains a total of 3,881 square feet of
rentable area and 1,941 square feet of rentable area, respectively, and the
Expansion Space in Building 22 contains 3,143 square feet of rentable area.

                28.3  Additional Terms.
                      ---------------- 

                      (a)   Landlord will not incur Liabilities to Tenant if
Landlord is unable to deliver vacant possession of any of the Expansion Space by
the required date if due to the holdover of a previous tenant or force majeure,
(but if due to a holdover Landlord will diligently attempt to deliver vacant
possession of that space as soon as reasonably possible), and Tenant's rights
and obligations with respect to that space will commence as soon as Landlord
delivers vacant possession.

                      (b)   When Landlord tenders vacant possession of any
Expansion Space to Tenant, that space will become part of the Premises, the
rentable area of the Premises will be increased by the rentable area of that
Expansion Space, and otherwise the Expansion Space will be treated in the same
manner as Additional Space under this Lease."

4.   No Other Changes.
     ---------------- 

     Except as set forth above, the Lease remains unchanged and in full force
and effect and there are no defaults by Landlord or Tenant thereunder.

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     IN WITNESS WHEREOF, intending to be legally bound, the parties have
executed this Amendment under seal as of the date first set forth above.

                                      FTP SOFTWARE, INC.
WITNESS:
/s/ Edward J. Rosner                  By:  Robert W. Goodnow, Jr.
- ------------------------                  ----------------------------
Name Printed:                            Name:   Robert W. Goodnow
Edward J. Rosner                         Title:  Vice President Finance
                                         Authorized Signatory

WITNESS:

____________________                  By:___________________
Name Printed:                            Name:
                                         Title:
                                         Authorized Signatory

                                      -5-

 
                                       NORTH ANDOVER MILLS REALTY

                                       By:  Niuna-North Andover, Inc.,
                                            general partner
WITNESS:

/s/ Josephine A. Uszynski                   By:/s/ Martin Spaggat
- ----------------------------                   ------------------
Name Printed:                                  Name:   Martin Spaggat
                                               Title:  Vice President
                                               Authorized Signatory

                                       By:  CIIF Associates, a Massachusetts
                                            partnership, general partner

                                            By:   Copley Advisors, Inc.,
                                                  managing general partner
WITNESS:

/s/ Thomas W. Mazza                    By:  /s/ Charles A. Valentino
- ----------------------------                ----------------------------
Name Printed:                               Name:   Charles A. Valentino
Thomas W.Mazza                              Title:  Managing Director
                                                    Authorized Signatory

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                                  EXHIBIT "A"
                                  -----------
                               "ADDITIONAL SPACE"

                            BUILDINGS #44E AND #44W
                                  FIRST FLOOR

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                                  EXHIBIT "A"
                                  -----------
                               "ADDITIONAL SPACE"

                           BUILDINGS #9, #9A AND #44E
                                  SECOND FLOOR

                                      -8-

 
                                  EXHIBIT "A"
                                  -----------
                               "ADDITIONAL SPACE"

                                 BUILDING #44E
                                  THIRD FLOOR

                                      -9-

 
                                  EXHIBIT "A"
                                  -----------
                               "EXPANSION SPACE"

                              BUILDINGS #9 AND #9A
                                  FIRST FLOOR

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                                  EXHIBIT "A"
                                  -----------
                               "EXPANSION SPACE"

                                  BUILDING #22

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                                  EXHIBIT "B"
                                  -----------
                         LANDLORD'S BASE BUILDING WORK

1.   ENTRANCE TO BUILDING #9A
     ------------------------
     a.   Designs and approval
     b.   Sitework
     c.   Walkway(s) and landscaping

2.   HVAC and MECHANICAL ISSUES
     --------------------------
     a.   Maintenance 'check-up' and servicing of all units
     b.   Install 'fresh air' HVAC intake(s)
     c.   Construct electrical rooms, as required by design
     d.   Install 'cable trays' for data & communications wiring
     e.   Existing lighting: replace light bulbs, check ballasts and check
          quantities of fixtures
     f.   Life safety equipment: including sprinkler, to comply with code
     g.   Electric consumption for FTP, other tenant and common spaces to be
          separately metered
     h.   Install new data/communications conduit from the rear of 
          Building #11 to Building #9A.  Tenant will compensate Landlord for
          this work.                   
 
3.   HANDICAPPED ISSUES
     ------------------
     a.   Design approval
     b.   Ramp from third floor of Building 44E to second floor of Building #9.
     c.   Other:  restrooms, corridors, etc.
 
4.   PASS-THROUGH BETWEEN BUILDINGS #44E AND #9
     ------------------------------------------
     a.   Make repairs/install spandrel glass at existing storefront frame at 
          West wall of Building #9             
     b.   Other:  Check-out and/or install lighting, etc.

5.   EXISTING BUILDING #9 CONCRETE STAIR
     -----------------------------------
     a.   Remove stair and in-fill second floor at opening

6.   MISCELLANEOUS REPAIRS
     ---------------------
     a.   Replace broken glass (if applicable)
     b.   Seal/caulk interior perimeter of windows to prevent air infiltration
     c.   Install new window/glazing at East end of Building #9A, where old
          (wooden) loading dock doors are removed

7.   DEMOLITION AND CLEANING OF SPACE
     --------------------------------
     a.   Remove miscellaneous equipment/materials/supplies from Tenant's
          premises
     b.   Remove birds from second floor of Buildings #9 and #9A

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8.   EXISTING RESTROOMS
     ------------------
     a.   General cleaning of restrooms in Building #9 and #44E
     b.   Make necessary repairs as required

9.   OLD HOIST EQUIPMENT (CRANE) IN BUILDING #9A
     -------------------------------------------
     a.   Inspect and make safe
     b.   Remove cable, but keep hoist (crane) in place

10.  MASONRY REPAIRS
     ---------------
     a.   Repair masonry chimney at East wall of Building #9A
     b.   Perform interior masonry repairs as required

11.  ROOFING
     -------
     a.   Inspect membrane roofing above Tenant's premises and make repairs as
          required

12.  DESIGN FEES
     -----------
     a.   Landlord will be responsible for all design fees that are associated
          with the work described in the preceding items #1 through #11

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