RBN Exploit is the source that revealed everything you wanted to know about the RBN and related enterprises.
Emerging Threats is an open source community project that maintains an excellent Snort signature set.
Spamhaus tracks the Internet's Spammers, Spam Gangs and Spam Services, provides dependable realtime anti-spam protection for Internet networks, and works with Law Enforcement to identify and pursue spammers worldwide.
Trendmicro provides home and enterprise security solutions as well as up-to-date information on viruses, spyware and their distributors around the web.
StopBadware are a leading authority on trends in badware and its distribution, and a focal point for the development of collaborative, community-minded approaches to combating badware.
McAfee Avert Labs has developed a general ranking system that indicates the severity of known global threats and how they impact the Internet, business operations, and home users’ systems.
Zone-H Internet Thermometer
The scope of this section is to show that the Internet (server side) is truly vulnerable. In order to do this, Zone-H think that the best way is to monitor web defacements. Why web defacements? Because they demonstrated over the past years that the web defacements are performed using the same techniques used by serious cyber-criminals when doing nastier things than a deface.
ThreatExpert is an advanced automated threat analysis system designed to analyze and report the behavior of computer viruses, worms, trojans, adware, spyware, and other security-related risks in a fully automated mode.
KnujOn is a multi-tiered response to Internet threats, specifically email-based threats. The success of this project is based on the cooperative efforts of business, government, law enforcement, security professionals, consumers, and average citizens. Knujon is a meeting point for all parties who wish to make the Internet a safer place. This multi-purpose e-fraud tool has significantly reduced junk mail traffic to various users and on the Internet in general.
SpamCop is the premier service for reporting spam. SpamCop determines the origin of unwanted email and reports it to the relevant Internet service providers. By reporting spam, you have a positive impact on the problem. Reporting unsolicited email also helps feed spam filtering systems, including, but not limited to, SpamCop's own service.
SiteVet is a tool aimed at the security research and web development community, providing historical and current data on Domains, IPs, ASNs and Cnets across a wide range of blacklists.
Bad Host provides free AS reports to help webmasters and security professionals keep their servers clean, and assist consumers in choosing a suitable web host.
FIRE is a service to identify rogue networks and Internet Service Providers. On a daily basis, reports are generated on this site that expose the dark side of the Internet.
Team Cymru is a non-profit Internet security research firm. They offer several excellent public services, such as an IP to ASN mapping tool, in addition to private cybercrime research.
UCEPROTECT offer an excellent 3-tiered spam DNSBL service at absolutely no cost.