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Details
Backfont.765
These are memory resident parasitic viruses, they hook INT 21h and write themselves at the end of EXE-files are executed.
Backfont.900,905
These are not dangerous viruses. They hook INT 8 and 21h. They contain no text strings, manifest themselves depending on their internal counters and the current year, month, day and only if EGA-adapter is present. You can see a rather interesting video effect: approximately 20 min after the virus activation all symbols displayed on the screen "flip", i.e. "/," -> "`". (shown approximately). The symbols remain in their places, only their view is changed. Approximately 10 seconds later the original state of the screen will be restored, next 10 sec. later the symbols will flip ones more etc.
Backfont.765,821
These are dangerous viruses. Upon every call of the ChDir DOS function (INT 21h, ah=3Bh) they set one of FAT cluster to BAD (pseudobad cluster).
Backfont.896
It's a harmless virus. It doesn't manifests itself.
Backfont.1172
It's a not dangerous virus. It hooks INT 8, 21h. Sometimes it decrypts and types the message in Russian. |