Next-Generation Nachi Worm Offers Political Message

The Internet is fertile with new and modified worms, but the most interesting is the next-generation of Nachi. The vigilante worm has gone strangely political.

"May you live in interesting times" goes the old curse. Times are interesting indeed in the world of computer security, especially this week. Every day brings another major worm or attack, maybe two, and the outlook looks even worse.

The last few days have shown remarkable fertility among computer worms, as new variants of MyDoom arrived on the Internet. A new worm on Wednesday began crawling the AOL Instant Messenger network. And a new variant of the vigilante worm Nachi arrived on Thursday.

By the time you read this, all of the above may be old news, overtaken by even newer variants doing crazier things.

Of course all of it is less scary than Microsofts announcement this week of a Link security hole in Windows that, as with the Blaster incident from last year, could allow for remote network infiltration without user action.

The most interesting, to my mind, is Nachi.B also known as Welchia.B. Some may remember the A version of this one that came out last summer in the wake of Microsofts DCOM RPC vulnerability.

Nachi.A spread through the DCOM RPC hole and then tried to download and install the patch to fix the hole. It also attempted to remove the Blaster worm, the most significant malicious exploit of that particular vulnerability.


Anyway, Nachi.B attempts to exploit these same holes and some others in order to spread itself. It then attempts to remove the MyDoom.A and MyDoom.B worms and undo some of the damage they cause, such as the overwritten HOSTS file. Nachi basically writes a blank one.

Finally, it attempts to download and install a Microsoft patch for a buffer overrun in the Messenger service.

So its trying to be helpful. Or so it would seem.

However, remember that Nachi.A was funny news at first, but it quickly became for many corporations a bigger problem than Blaster. I note that its still out in the wild.

Nachi.B could easily prove to be as bad. Some persons no doubt will spread it intentionally because its a "good" worm.

Next Page: Decoding Nachi.Bs Political Message.