Technology Blog

Dr. Dave, author of the Spam Karma WordPress antispam plugin, has posted an
interesting article about new weblog-spammer
tactics:

These spams do not present most of the idiotic traits of their lower
colleagues: they do not try cramming hundreds of URLs or inserting hundreds
of easily spotted junk keywords in the comment content. Instead, they use
only the dedicated name and homepage fields to sneak in spam URL and
keywords. The comment content is often perfectly innocuous, sometimes even
topical (by copying parts of another comment or a trackbacking post). All in
all, these spams could easily be missed by a human moderator who wouldn’t
look carefully at the contact name and URL.

(Thanks to Kelson Vibber for the pointer
to this.)

In other words, he is noting what we noticed in email anti-spam; that what
works well one year, is likely to degrade over time as the spammers attempt to
evade it, and one has to keep working to keep up.

The best term for this appears to be adversarial
classification. Anti-spam
activities fall into this category, and it often means that classic text
classification algorithms aren’t suitable — after all, the Reuters-21578
dataset
never tried to evade your classifier

In a similar vein, this MS research
paper is interesting:

Previous work on adversarial classification has made the unrealistic
assumption that the attacker has perfect knowledge of the classifier. …. We
present efficient algorithms for reverse engineering linear classifiers with
either continuous or Boolean features and demonstrate their effectiveness
using real data from the domain of spam filtering.

It’s akin to John Graham-Cumming’s work looking into how a spammer could get
past a bayesian filter “from the outside”, but with more techniques, and
examining MS’ MaxEnt algorithm, too. PDF
here, well worth
a read.

(By the way, I’m in the process of moving house, so if you send me an email, it
may take a while for me to reply. This situation is likely to prevail for the
next few weeks, for what it’s worth — fun.)

adversarial classification anti spam maxent papers spam karma weblogs wordpress

This post was written by Justin, source: Weblog Spam and Adversarial Classification