Malware is hidden software that sends out emails. Most spam that people receive today is actually sent from other people's machines that has been infected with malware.
Malware is quite a sophiscated piece of software. Most anti-virus software wont detect that your PC is secretly sending thousands of emails.
The malware programs often hides inside system drivers and will make a direct connections to your internet as to comletely bypass any PC firewall's. Your system will be completely unaware that emails are being sent.
The only way to know if emails are being sent is to look at the raw data being sent from your network connection, or to look at the internet data going through your modem.
Advanced users can help to fix this by blocking and log port 25 at the modem.
We've tested quite a number of programs which apparently help fix these issues, and currently this one below is the only one that we are aware of which successfully removes malware.
> Mailware bytes <
Even better, its completely free to scan and fix all problems. The paid version will actively make sure you dont get any more.
If everyone today used this software, we think spam could be reduced by 90%!