Anti-Virus Turned Trojan

A medieval knight wearing a clunky metal armor could hardly move if left on his own. He needed a horse to carry him around. In our age the CPU cycles of our computers are increasingly used for protection.

Recently one of our computers became almost useless for Internet surfing. Pages that used to load like lightning suddenly were a pain to look up. This happened overnight on a quite new desktop box running Windows XP. I checked the network card, but streaming video over the local LAN was no problem. Also, Linux boxes on the same LAN had no problems.

A little later I updated a seldom-used laptop to Windows XP SP3. Now I had a chance to do controlled measurements. After the update the laptop displayed symptoms similar to those of the desktop box. The main page of a daily newspaper took around 40 seconds to load with Firefox 3 (twice the time with IE). The main page uses little or no caching. The same page took less than 5 seconds on a Linux box using Firefox 3. In fact, most of the page was rendered in 2 seconds. This means there was a 10 to 20-fold increase in response time.

When loading the page I noticed Firefox (and IE) saying “Waiting for (the web site)…” The pause lasted 10 to 15 seconds. Being inside a very restrictive firewall I decided to uninstall the anti-virus program, Trend Micro PC-cillin. Lo and behold, now the newspaper page loaded like it used to, in less than 5 seconds.

So, be selective about protective software. An anti-virus product may add so much overhead to Internet access that you simply can’t do your job. This is anti-virus turned trojan.