- Crewl Underground Madness
- Belgian group specialized in computer and network (in)security, hacking, coding and phreaking.
- Cult of the Dead Cow
- Offers weblog, team background, tools and BackOrifice downloads, and news archive.
- Group of hackers in the United Kingdom. Information about meetings, projects, and links to personal pages.
- Nomad Mobile Research Centre
- Hacker lab engaged in vulnerabilities research. Security papers, full disclosure advisories and current projects. Also features a FAQ on hacking techniques.
- Toronto 2600
- Canada's Largest Hacking and Phreaking meetings. Picking up where the great Hack Canada left the Edmonton 2600 meetings in 2002.
- Hack This Site!
- Hack This Site is a free, safe and legal training ground for hackers to test and expand their hacking skills. More than just another hacker wargames site, we are a living, breathing community with many active projects in development, with a vast selection of hacking articles and a huge forum where users can discuss hacking, network security, and just about everything. Tune in to the hacker underground and get involved with the project.