MyDoom virus alert

The MyDoom virus is hammering on all Windows doors since yesterday. A part of the payload seems to be DDossing SCO, the company suing IBM and the like for supposedly using their proprietary sourcecode in developing the Linus OS.
This morning, arriving at work I found the virus already blocked a couple dozen times by our mailserver. And this even without updated antivirus files. The problem with viruses, of course, is that they can spread so fast, that automatic update intervals for virusscanners don't suffice to stop them. Also in this case, I expect a lot of company were too slow updating their files, and the virus already spread on their networks. At least, I've always been very happy about our strict policy of blocking .exe, .scr, .pif etc by default. Compiled exes are just not meant to be distributed by email. And in case someone really has to sent an exe, then they know that adding the txt extension will help. This measure of preventive blocking is quite successful, as even after about five years of mass email viruses (as far as I know, the Melissa virus was the first real massmailer, correct me if I'm wrong), they still pose a big threat.