Ablynet is a social bookmarking site powered by Pligg open source CMS. Beside promote http://www.ablynet.com/, I would like to share the effective way to block spammer. 1. Get Akismet api key, although this is more popular for wordpress CMS, but it is still effective in Pligg. 2. Stopforum spam list to my site, although it mention forum but you can download the spammer list for your blog and other website. Through http://www.stopforumspam.com/downloads/ you can download it according to email list, ip list and user name. 3. To avoid wrongly spam kill, I added custom field question for each bookmark submission. Obviously robot submission will skip the custom question. Advise to adjust the question every 2-3 months. 4. Captcha text registration, on and off switch it to Captcha word, mathematics question, custom question. I believe those auto-spam only targeted to single matter calculation. 5.Spam Trigger -pre added dictionary keywords to system, auto block content which have sex, escort..... Of course above matter cant avoid human spam, but it still effectively to block reduce 90% of robot spam.