We have had some responses and advice on handling the problems of spam and viruses in e-mail following my recent Tech Talk column on challenge/response, a method that some people like and others do not. The problem is unlikely to be resolved for some time to come. ? I entirely agree with you on challenge/response systems. They seem to create as many problems as they solve. Although David Webb says a Bayesian filter is an ineffective solution, it is one that works well if used in conjunction with other sophisticated filters. In our product Spam Blackout, we employ no fewer than six different filters as plug-ins, which gives about a 95 per cent success rate. These are: 1. Bayesian filter 2. Friends/enemies list (blacklist/whitelist) 3. Keywords 4. Internet blacklists (real-time look up on internet spammers' databases) 5. Tracker killer (blocks e-mail with tracking information, iframes, white text, unusual tags, random text and phishing URLs) 6. Country blocker, which blocks irritating e-mail from Nigeria, for example. (Perhaps blocking entire countries could be a dictator's dream come true.) In addition, Spam Blackout has a comprehensive list of attachments to allow or quarantine and it can optionally zip attachments to conserve space. Spam Blackout can be configured to filter e-mail for an entire office so there is no need to install on every PC, and it can receive e-mail from POP, IMAP and Hotmail accounts. Greg Spinos, Sheung Wan More information on Spam Blackout is at: www.itexpertsnet.com/spamblackout . Another reader sent in a message saying Mozilla is hard at work on Thunderbird, the open-source mail client: Given the upsurge of spam and the reluctance or apathy of Hong Kong internet service providers in solving the problem, I believe users must use better tools to get their mailboxes under control. Thunderbird comes with an advanced adaptive junk mail filter which learns what your spam/ham mail is and then automatically moves spam to a junk folder or deletes it. Unlike Outlook Express/Out-look, it is not vulnerable to all the worms/viruses which rely on ActiveX or Outlook bugs. Yusuf Goolamabbas, Cyberport Tech Talk is trying to get some solid information on how Hong Kong's ISPs are trying to deal with spam. Because so many people hate it and it seems unstoppable, the ISPs are often attacked for not doing enough. It is a complex problem for them. In the meantime, we have software solutions.The mail filter that comes with Apple's OSX is about 99 per cent accurate. Thunderbird is free but Spam Blackout will cost about HK$250 and works only on Windows 98, NT, 2000 and XP. Thunderbird information and downloads are at: www.mozilla.org/products/thunderbird . As for the unconcerned ISPs, last week, Pacific Supernet launched a spam filtering service for its users. Senior marketing executive Gloria Lam said Supernet would charge $10 a month for the service. Questions to Tech Talk will not be answered personally. E-mail Danyll Wills at firstname.lastname@example.org .