+ 0 Votes Eggs and baskets beck.joycem 2 years ago There's every reason to run multiple threat-detectors.It's simple: they were all designed, written and maintained by human beings, and are therefore imperfect. When I disinfect a computer I usually use AVG first, then MBAM, SuperAntispyware and Spybot. Each one will likely find something the others didn't. I keep using those, and others, until they come up clean.The general rule is to have one antivirus, they have a tendency to fight each other. No need to pay for one, the freebies like AVG and Avast are good. Then use other free anti-spyware for regular scans.As to where it all comes from - I wish I could say for certain exactly where every infection came from on any particular computer. Apart from your security software it's vital to keep up to date: Windows, browsers, Java, Flash, Shockwave, Adobe Reader, MS Office - any really common software is a potential target.