DCOM Attacks are speculative (which this is), not targeted and tries to exploit a vulnerability in out of date OS, if your OS is up to date then you aren't vulnerable to the exploit. That doesn't stop them (usually someone from the same ISP with an infected computer) trying to see if it can infect others.
Your firewall should be the first line of defence in this, but avast also monitors common attack ports using the Network Shield, ideally the firewall should block it and avast wouldn't know about it, but for whatever reason avast is first in line over your firewall.
Edit: Unfortunately that techtips article is old and relates to avast 4.8.
There are inaccuracies in it. Switching of DCOM won't stop the speculative attempt to exploit the system. Also the implication that this is as a result of a virus or worm on your system is a giant leap in speculation as there are inbound attacks. If they were outbound attacks they are likely to show a different MAL:URL alert something trying to connect to a malicious site.
So my advice would be to ignore this old advice for avast 4.8, aside from any other inaccuracies.
