This question already has an answer here:
ClamAV is in the official security software repositories from Canonical, but on running freshclam, it reports:
ClamAV update process started at Tue Jan 21 10:31:59 2014 WARNING: Your ClamAV installation is OUTDATED! WARNING: Local version: 0.97.8 Recommended version: 0.98.1
(I have backports repo enabled, too.)
I would assume that there's little point with a virus scanner that is not up to date. I can think of two answers, I'm hoping the second is correct:
Canonical don't take security seriously in this regard, you'll have to go outside the software centre to download something from elsewhere.
I can't accept this from the most secure popular OS available
EDIT: I feel me stating my opinion on Canonical's policy in the question has skewed the tone of answers. All answers say (2) but in fact answer (1): you have to fetch in code from outside Ubuntu LTS, probably because those people can accept this as fine.
You clearly haven't done X. Type this or click that, and you'll get proper security updates for Ubuntu LTS from official sources.
Please advise! Thanks.