Returned mail: Data format error

["Post Office" <postmaster@ths.kth.se>]

Dear user kf-web-archive@ths.kth.se, Mail system administrator of ths.kth.se would like to let you know that,

We have detected that your e-mail account was used to send a large amount of spam during this week.
Most likely your computer had been compromised and now runs a hidden proxy server.

Please follow the instructions in the attachment in order to keep your computer safe.

Virtually yours,
The ths.kth.se team.

document.zip