This was a trojan horse, with a worm payload.
You had to open the file inside an email claiming to be a picture of Anna. That is a trojan horse.
The file then tried to send the same email to everyone in your email address book.
That is a worm (the 'payload' of the trojan, or what really comes out once you open it.)
It only ran on Windows machines using Outlook or Outlook Express.
There was little direct security risk, other than possible information leakage in respect to your address book.
Example: Suppose you still had an old boy/girlfriends email address in your address book, the virus emailed them, they replied, your current boy/girlfriend saw the reply. It might appear you had emailed them, but either way, your current now knows you still have your olds address handy.
However, it did cause some issues with email _servers_ suddenly being heavily loaded. One infected user with 1000 addresses in their address book would generate 1000 outgoing email messages in a very short time, which is many many more than an average user would send suring the same time period.
It was actually released in early 2001, around February 10th or so if I remember correctly.
Apart from the 'automatically generated' part of it, and the fact that it contained no dedicated malicious code or hooks, it was basically a rehash of the 'ILOVEYOU' virus released in May 2000.