* How not to handle spam filter false positives
One of the more troubling aspects of the deluge of spam we are all suffering is that anti-spam techniques can turn into denial-of-service techniques if they are not handled properly. I recently received a sad story bearing on this subject from a reader who asked to be kept anonymous for fear of repercussions.
The following is the reader’s text with minor editorial changes:
“I’d like to tell you about a problem we’re facing with the way our administrators are handling false-positives in their anti-spam solution.
“In March 2004 we had an average of 24,740 items of mail entering daily. Of these, 9,697, or 39%, were identified as junk by the appliance for spam filtering.
“On average, there were complaints about 16 pieces of mail per day that were subsequently released as not junk. The system administrators calculated that the false-positive rate was 16 out of 9,697 or about 0.16%.
“I disagree with the last statistic since most people don’t realize that mail intended for them hasn’t arrived. They don’t even know that the e-mail is being filtered because the e-mail administrator made no announcement about the tool’s implementation. I personally realized that something was wrong when many of the mailing lists I subscribe to vanished. It was only after a few weeks of lower activity in my mailbox that I realized that they had stopped arriving. I had people from abroad who correspond with me on a somewhat regular basis calling me asking why I didn’t respond to their letter, to their reminder about the original letter, and to their second reminder! That was the way I found out that the filter was activated. And I am an IT senior staff member.
“This product doesn’t let the individual user go in and see the mail that has been classified as junk. You have to go and speak with the administrator if you think something didn’t arrive. As a company with 11,000 users and multiple sites this is unrealistic.
“It also doesn’t let you have any individual control, like a personal blocking list. It doesn’t let an employee set his own level for filtering. You either filter out all the mail for an individual, or let it all flow into his mailbox. MSN Hotmail has a better setup for its millions of users. MSN Hotmail lets a user choose different levels of filtering; you can return letters to your inbox by yourself; and you can tell the filter that a particular letter is not junk for future reference.
“The absolute worst thing was a comment by one of the IT managers in a recent management meeting when his response to my criticisms was, ‘If an employee doesn’t know that he didn’t get a letter then it means that it wasn’t an important letter and he can do without it.’”
No further comments are necessary. Read it and weep.
