1. MX Toolbox
The MX lookup is done directly against the domain's authoritative name server, so changes to MX Records should show up instantly.You may also check each MX record (IP Address) against 105 DNS based blacklists . (Commonly called RBLs, DNSBLs)
2. Akismet
Akismet is an advanced hosted anti-spam service aimed at thwarting the underbelly of the web. It efficiently processes and analyzes masses of data from millions of sites and communities in real time.
Powerfuzzer is a highly automated and fully customizable web fuzzer (HTTP protocol based application fuzzer)Currently, it is capable of identifying these problems:Cross Site Scripting (XSS),Injections (SQL, LDAP, code, commands, and XPATH),CRLF,HTTP 500 statuses (usually indicative of a possible misconfiguration/security flaw incl. buffer overflow)
4. Acunetix
Acunetix Web Vulnerability Scanner automatically checks your web applications for SQL Injection, XSS & other web vulnerabilities.
5. Vaultpress
VaultPress makes it easy to keep an up-to-date backup of your site with both daily and realtime syncing of all your WordPress content. To ensure your site stays safe, VaultPress performs security scans daily and makes it easy to review and fix threats.
6. Sucuri
It detects unauthorized changes to network (cloud) assets, including web sites, DNS, Whois records, SSL certificates and others. It is also heavily used as an early warning system to detect Malware, Spam and other security issues on web sites and DNS hijacking.
A simple yet effective anti spamming plugin for chats.
Be it comment spam or contact form spam, this plugin blocks spam from entering your Wordpress database.
9. Clean Talk
A cloud-based anti spamming plugin for Wordpress.
10. Anti-spam Bee
A potent plugin that protects your Wordpress website or blog from spammers.
11. AntySpam
An anti-spam plugin compatible with Wordpress Multiuser, bbPress, BuddyPress.
12. WangGuard
A free, basic and simple anti-spam filter for Outlook with an option to add customized servers.
13. SpamBayes 1.1a6
A free add-on for popular mail programs like Thunderbird, Outlook, Yahoo, Gmail, etc.
14. JunQuilla
An add-on for thunderbird to filter spam mails showing junk status as well.
15. Spam Fighter
A free and efficient anti-spam filter for Thunderbird.
16. Mailwasher
Free and reliable spam filter software that works with almost all email programs.
17. Spychecker
A free anti-spyware that takes care of your online privacy.
18. Spam Bully
Spam, Viruses, Malware - say goodbye to all of it with Spam Fence.
19. Spam Fence
An anti-spamming tool for Windows that works with Windows Mail, Outlook, Live Mail & IMAP.
20. Spamato
A spam filter tool available as an add on for Thunderbird and Outlook.