I keep getting a message from Avast that says it has blocked [something, it varies] [mal] and \\\globalroot\systemroot\svchast.exe.
Some sites say TDSSKiller will fix it. Is TDSSKiller ok to use?
I have Avast and occasionally it reports that it has blocked a certain site. That means that it is preventing you from going to that site because it might damage your computer...it doesn't mean that malware has been installed. Are you getting this Avast message randomly or only when you try to visit a specific site or sites?
TDSSKiller is a fix for a specific rootkit. What makes you think this relates to what you are describing? My view is that you should never run such software unless you are sure it's needed. While TDSSKiller is provided by a reliable anti-virus company -- Kaspersky -- it has been known to mess up some users' computers.
I would only advise using it with the guidance of the support forums that specialize in malware removal, like LzD.
Added by the Troj/Lineage-AV password-stealing Trojan for the online game Lineage.
Characteristics of Troj/Lineage-AV
Turns off anti virus applications
Installs itself in the registry
I'd follow all instructions at the link below for Malware removal and have more complete scans done.
Here is a link that might be useful: malware-removal/log-posting-instructions
Question in OP is moot. Everything quit. We did a restore.
This was the computer on which we watched TV. Hulu, network archived stuff, CSPAN etc. We were seeing the message from Avast at the beginning of each and every commercial or the pauses where a commercial would have been expect with live TV. No more after the restore. Nothing was lost.
Ok. So perhaps you got lucky and Avast blocked it.