This virus is based on the Vienna virus, but the author (whose identity is known) has made considerable modifications to it. The most significant is that the virus is now encrypted. The virus adds 1260 bytes to the files it infects. The first 39 bytes contain a simple decryption routine, similar to the one used by the Cascade virus. There is one important difference, however. A variable number of short (1- or 2-byte) instructions are added between the decoding instructions. The extra instructions do not affect the operation of the virus - they are only placed there in an attempt to prevent virus scanners from using identification strings, which makes it a little harder to detect the virus.
Once detected, the F-Secure security product will automatically disinfect the suspect file by either deleting it or renaming it.
Detailed instructions for F-Secure security products are available in the documentation found in the Downloads section of our Home - Global site.
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The Casper virus is created by modifying the source code to V2P1. It contains the following text.
Hi! I'm Casper The Virus, And On April The 1st I'm Gonna Fuck Up Your Hard Disk REAL BAD! In Fact It Might Just Be Impossible To Recover! How's That Grab Ya! [GRIN]
The virus will indeed activate on April 1st and try to format the boot sector, with incorrect parameters. The code seems to contain an error, though.
By the same author as V2P1, the only significant difference is that the length is now variable.
The last virus in this series. It uses a much more complex self-modifying encryption method.