[RD (OP)]

I've had Microsoft security essentials for over a year and this is the first nasty it has detected ...

 [ Invalid Attachment ]

http://www.microsoft.com/security/portal/Threat/Encyclopedia/Entry.aspx?Name=TrojanDownloader%3AWin32%2FPonmocup.A&ThreatID=-2147337205

The infection was via a respectable "Times online" link.

[SeanB]

Most likely a third party ad "partner" that downloaded the malware. A very good reason to not use IE and install Firefox, along with NoScript and Adblock. Another I use is Ghostery.

[RD (OP)]

Most likely a third party ad "partner" that downloaded the malware. A very good reason to not use IE and install Firefox, along with NoScript and Adblock. Another I use is Ghostery.

I was using FF4 with with NoScript and Adblock Plus active when this infection occurred.

The only atypical thing was that I had adobe reader open with javascript enabled at the time,
normally I have javascript turned off in it, see ... http://www.zdnet.co.uk/news/security-management/2009/04/29/adobe-reader-javascript-security-flaw-emerges-39646143/