[CentOS] How to check for rootkit, troians etc in backed up files?

Hi,

there is a remote (VPS) Centos 4.2 server which *may* have been compromised. Reinstalling everything from scratch isn't a problem, it may even be an occasion to improve a few things, the question is another.

There are backups of necessary shell script, ASCII configuration files and more or less important email (maildir format, if it matters) including messages with binary attachments in .doc, .pdf, .jpeg and other formats. What is, in the context above, the best way to make sure that **those** backed up files (which _must_ be put back on the server after reinstall) do not contain any rootkit, troian, virus, whatever? Which Centos / linux tool you'd recommend for this specific case?

TIA, Marco