And another one in the same direction:

The most determined cyber criminals don't necessarily work fast when they breach a network, and their infiltration is often silent and undetectable. But it's this brand of "low and slow" targeted attack that can also be the most deadly, security experts say:
http://www.darkreading.com/security/attacks/showArticle.jhtml;jsessionid=UFNEPFUNCGARMQSNDLPSKH0CJUNN2JVN?articleID=212701434

Have alook also at the following blogpost about Microsoft SIR:
http://blogs.technet.com/ms_schweiz_security_blog/archive/2009/01/12/the-latest-microsoft-security-intelligence-report-v5.aspx 

Urs

The Microsoft Security Intelligence Report (SIR) provides an in-depth perspective on the changing threat landscape including software vulnerability disclosures and exploits, malicious software (malware), and potentially unwanted software. Using data derived from hundreds of millions of Windows users, and some of the busiest online services on the Internet, this report also provides a detailed analysis of the threat landscape and the changing face of threats and countermeasures and includes updated data on privacy and breach notifications. The fifth volume of the report is now available:

SIR Volume 5 (January through June 2008) and Key Findings Summary
http://www.microsoft.com/security/portal/sir.aspx

Urs

Sunbelt Software has released its monthly data dump that charts the most commonly observed malware and spyware threats, and, as has been the case for a good while, trojan attacks continued to lead the way across the Top Ten rankings during Dec. 2008.
http://securitywatch.eweek.com/exploits_and_attacks/trojans_dominated_malware_threats_in_dec_08.html

Have alook also at the following blogpost about Microsoft SIR:
http://blogs.technet.com/ms_schweiz_security_blog/archive/2009/01/12/the-latest-microsoft-security-intelligence-report-v5.aspx 

Urs