This is a Vienna-derived virus, virus, but it marks infected files by setting the "month" field to 13, instead of setting the "seconds" field to 62. W-13 has been reported to have originated in Russia as well as in Poland.
A 507 bytes variant with some bugs corrected is also known.
Disinfection & Removal
CSSR 528, IKV 528
This East-European virus is related to the W-13 viruses, but it has not been fully analyzed yet.
This is a minor modification of the 507 byte variant mentioned above. It will set the "month" field to 12, which makes it less obvious, as 12 is a legal value, but this also makes all files created in December immune to infection.
A 494 byte variant from Poland - Not yet analyzed.