This is a virus detection. Viruses are programs that self-replicate recursively, meaning that infected systems spread the virus to other systems, which then propagate the virus further. While many viruses contain a destructive payload, it's quite common for viruses to do nothing more than spread from one system to another.
The W32/Sality.o detection covers PE files that are partially infected with a W32/Sality variant. However, unlike other W32/Sality infections, W32/Sality.o does not contain the core W32/Sality.dll component. The entry point of such PE files has been overwritten by the Sality virus, and the original entry point is encrypted within the last PE section of infected files. Even in this state, W32/Sality.o infected files are repairable.
At the time of this writing, the only W32/Sality.o infected files received by AVERT are variants of the W32/Bagle virus (these are what is known as cocktails, multiply infected files; in this case:
( W32/Sality.o ( W32/Bagle ))
Upon removing the W32/Sality.o infection, W32/Bagle is then identified.
W32/Bagle.dt@MM is one such cocktail known to be spreading.
W32/Sality.o may not be viable in W32/Bagle cocktail form. However, it does not prevent W32/Bagle from replicating successfully.
Use current engine and DAT files for detection and removal.
Modifications made to the system Registry and/or INI files for the purposes of hooking system startup, will be successfully removed if cleaning with the recommended engine and DAT combination (or higher).
But in some particular cases, the following steps need to be taken.
Please go to the Microsoft Recovery Console and restore a clean MBR.
On Windows XP:
On Windows Vista and 7: