McAfee has patched a vulnerability in its SaaS for Total Protection hosted anti-malware service that seems to have been misused by spammers to make users' computers spew out spam.

The flaw allowed attackers to use affected machines as an “open relays”, but didn't make available to them the data contained on the computers, said the company.

The vulnerability was discovered after a number of McAfee customers complained of having had their email blocked and IP addresses put on anti-spam blacklists. Fortunately, it took only a couple of days for the company to push out a patch for the issue and the customers' software to be automatically updated.

Another vulnerability - one which would allow an attacker to misuse an ActiveX control to execute code - was also detected in the SaaS for Total Protection solution this week, says the company, but a previous patch "cuts off the exploitation path for this issue, effectively reducing the risk to zero."

According to McAfee, the two bugs were present only in that particular service, and neither of them allowed attackers to access the data that customers have on their machines.