Brennan’s Blog

Over the last couple of weeks one of my servers became sluggish and the web server became completely unresponsive. Initially I saw the Spam Assassin process was chewing up the processor. Today I saw that a distributed attack was hitting my WordPress installation as spam comments were immediately deleted by Spam Karma. The server status was showing various IP addresses hitting the comments post page which would max out the number connections I allow for the web server. To overcome these attacks I am trying out the Apache DoS Evasive Maneuvers Module which manages an automatic blacklist which will stop these frequent hits from these remote servers. I have also limited the Spam Assassin service which should make it much less likely to allow it to be the resource hog it has been lately.

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In the last week I have noticed a greater amount of spam getting passed the spam filters. I predict that it will only dramatically increase before January. According to this Iron Port study, 80% of spam is coming from zombie computers. The zombies have been quietly infected with a virus so they can be used by a remote server to send out spam emails. And cleverly enough, each zombie may only send out a small number of messages so it goes undetected by the user and their ISP. It works because there are literally thousands of these infected zombies out there.

This sad state has been brought on by the fact that easily infected computers sit idle on constantly connected broadband connections. Any number of exploits could have compromised these computers. Typically these infected computers are running a variation of Windows which dominates the home desktop market which has been plagued by viruses and spyware these last few years. But there is hope that this major source of zombies will soon disappear.

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Email has become too unreliable. Over a year ago I started to forward my email into a Gmail account to get a great webmail interface and to shield my inbox from the increasing amount of spam that I was not able to avoid. It seemed to help at first, but with every method employed to block the unwanted messages, the spammers would develop a way to overcome it. Initially you could run an analysis of the words used in an email to create a spam ranking. The male enhancement and stock trading terms were commonly used in spam messages, but gradually the spammers became more clever. The would change the letters to symbols, like an @ instead of an A. But the word analysis eventually adapted and learned to block them.

Now the latest measure used by spammers is to fill the message with a passage from a book, or something pulled randomly from a website through a search engine. By filling the message with good words, the bad words were watered down and the emails would get through. But as you mark those clever messages as spam you increase your chances that genuine messages would be blocked.

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I have been actively fighting spam lately. For a long time I have been just using the Apple Mail client which has a nice spam filter, but I still get a lot of mail. And since I run my own server with many users I find the amount of spam takes up a great deal of disc space. So I have been trying various techniques to block unwanted mail.
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