A mass mailing worm has been discovered which attempts to infect computers by using old Windows exploits, according to security firm Clearswift.
The W32/Reatle worm has appeared in significant numbers, the company said in a statement.
The new worm targets unpatched systems.It is delivered via an email attachment and attempts to infect computers using two old vulnerabilities: DCOM.RPC and LSASS.
The threat was not new, Clearswift said. The vulnerabilities had already been addressed by Microsoft back in August last year.
W32/Reatle appears to disable installed antivirus products and attempts to mount a Denial of Service attack on the Symantec website, Clearswift said. Several hybrids of the worm have already started to appear.
The company said the worm was of a low to medium threat level.
Clearswift has advised Windows users to ensure their systems are kept up to date with the latest patches. For complete protection, users should block all executable files in email, just to be sure, a Clearswift spokesperson said.