| Heise Security | Security news of the Heise publishing house |
| SSL test | Check SSL connections |
| alternative SSL check | Condensed SSL check |
| MxToolbox | Network diagnostic and lookup tools |
| Insecure.org | Links, tools, infos from the developers of the nmap scanner |
| CERT | Security reports and mailing lists |
| SecurityFocus | Bug reports and mailing lists |
| CVE | Common Vulnerabilities and Exposures (Bug Reports) |