Win32/Coke.22231.A was sent to several anti virus researchers at the end of May 1999.
Coke works on Windows 95 and 98 (its bugs will not let it work too long on Windows NT, but it is able to infect files under NT). The virus infects both Portable Executable applications and Office 97 documents and it is polyrmohic in both cases. Its first polymrophic decryptor is placed in the code section of the PE applications in 8 pieces similarly to the One_Half virus. Coke is slow polymorphic, multi-threaded and uses multi-layered polymorphism and encryption in PE applications.
The virus is able to mass mail itself to several locations. This can happen when the user sends a mail. The virus hooks a MAPI function and attaches an infected attachment to all out going mails from the machine. Additionally the virus sends a mail with an infected attachemnt each time when the user visites a web page which has a "mailto" reference. The virus keeps a CRC32 list in a file on the machine about the addresses it sent itself too. Therefore only one copy will be posted to each locations.
There is nothing really new in this virus, but the combinations of all these techniques makes it uniqe and very complex.
Once detected, the F-Secure security product will automatically disinfect the suspect file by either deleting it or renaming it.
Technical Details: Peter Szor, F-Secure, 1999