group 4 trojans

norton recently found and resolved 5 high-risk trojans on my system:

 

f.class

vmain.class

patchers.class

cloners.class

debuggr.class

 

I don't know where these came from, and other people say that they have found them also, in this group. Afterwards, i ran malwarebytes scan in safemode and also it found 5 more infections.

 

How do I know if my system is safe and clean? Where did these trojans come from, and should I be worried? Why didn't norton block them in the first place?

 

I had the virus Tidserve. a month ago, and used the zip file tidservekiller to remove it. could it be remnants of that?

 

please let me know whether it is actually resolved, or whether i need to take action.