[comp.virus] Self-modifying applications

) (11/22/89)

In issue #246, Joel Glickman writes...

>From:    joel_glickman@MTS.RPI.EDU
>Subject: Potential Virus? (Mac)
>I have just recently noticed a problem on my Mac. After using Cricket
>Graph I checked the last modified date and the program had just been
>modified.  After noting this, I began checking other programs and
>found that my copy of Versaterm Pro was also being modified every time
>I ran it. It was at that point that I checked these programs on other
>people's Macs in the office and saw that these programs were not being
>modified on some, while they were being modified on others.. I am
>running Gatekeeper and Vaccine and have checked these programs with
>Disinfectant and they report no trouble.
>My question is: Should these programs modify themselves when I just
>run them.  All I do is run them and quit immediately and they are
>modified??? Do you think I have a virus problem???
>Joel Glickman
>Rensselaer Polytechnic Institute.

Some programs DO modify themselves while running, the important thing
to remember is that these modifications are usually made to the data
fork of the application.  Most virus detectors look only for attempts
to write to resource forks.  (I don't know about Gatekeeper, perhaps
its author could let us know?)  It still seems strange that other
people were not experiencing the same problems as you, but that
doesn't necessarily mean a virus.  To quote Douglas Adams "DON'T
PANIC", as many others do.  Here are some things you can check:

        1.      The other people you are working with may have locked their
                copies of CG or Versaterm Pro, preventing them from being
                modified.

        2.      Make sure Vaccine is running, look in your control panel and
                see that the protection is turned on (incidentally, when you
                alter the preferences for Vaccine, the size of the file
                changes, since Vaccine has no "preferences" file)

        3.      Try replacing your cricket graph with someone else's, see if
                the problem persists.  Likewise for Pro.

        4.      Try reinstalling your system, use the same release as those
                coworkers of yours who are not experiencing this phenomenon,
                again, see if the problem persists.

        These are just ideas, they're not carved in stone, but they may
provide some insights...  good luck!

                                        -- Chuck Seggelin
                                           Academic Computing Services
                                           SMU
ACSCDS@SEMASSU.BITNET           "Opinions expressed are MINE alone!!!!"