Security threat detected by my cable operator but I can't find it

Question

I received the following email from Cogeco this morning and they are going to shut me down soon if I can't deal with it. From my research at McAffee and Symantec it appears to something that only Windows users would get. I am confused. How can I detect a problem on my Mac?
You are receiving this email as Cogeco's network security dept has received reports of atypical traffic from your system that is indicative of malware (ie: a virus or trojan). Your system(s) are exhibiting symptoms of The Downadup (aka: Conficker) malware – see http://www.f-secure.com/v-descs/wormw32_downadupa.shtml for more detailed info.
Some items to note about The Downadup malware,
1. This malware could have been prevented by ensuring your Windows system(s) is updated regularly. In particular Cogeco recommends you ensure Windows Auto Update is enabled on all systems in your household – see http://www.microsoft.com/protect/computer/updates/mu.mspx for further info
2. This malware can also propagate via USB drives, if you are using a USB external drive please review http://support.microsoft.com/kb/953252 for more on how to disable USB autorun feature in Windows
For more information on how your system could be hijacked for these purposes see http://en.wikipedia.org/wiki/Zombie_computer
If you are unable to contain and/or investigate this threat immediately we request you temporarily power down or disconnect your system from the internet until you are able to further investigate. To prevent any possible interruption in service we require a follow up email within 24 hours - what malware you found, alternate reasons for this activity, what actions you are taking to prevent further incidents.
If you do not have access to an up to date security scanner or you would like a second opinion you can run a free online security scan at http://www.cogeco.net/security - you may also be interested in Cogeco's Security Services which are free for most customers. Alternately Windows users can visit http://www.microsoft.com/protect/support/default.mspx for further information on system security.
*Remember that security scanners need to be updated with new signature files frequently and Windows operating systems need to check for critical security updates on a regular basis.*

Answer 1

If you have a Windows virtual machine (VMWare or Parallels) or use Boot Camp to load Windows on your Mac, then it is possible. You should treat the virtual machine or copy of Windows you use in Boot Camp per their instructions. Window will always require additional anti-malware software.
If you have a PC with Windows on your home network, that's a possible source of the problem. Also, if you use a wireless network and it's open, someone nearby with an affected PC might be infected and causing the problem (Cogeco couldn't know whether it was your computer or someone else's, only that it came through your network connection).
If you don't have any of these things, then there's some confusion. You Mac system doesn't support the cited malware - it simply can't run on it. In that case, there's several possibilities: the Cogeco e-mail is fake (perhaps a phishing attempt to try and coax you into providing personal information or downloading software), or Cogeco's traffic analysis is wrong (the software used improperly interpreted some other activity as the virus, or the operator of said software has misinterpreted the results).
In any case, you need to contact Congeco (by telephone) and point out that you don't use Windows and are not able to run Windows malware (even if you wanted to).