Hello,
Please check if you are not infected. The Logs clearly state that you are infected with W32.Downadup.B
Downadup (conficker) is quite old virus. If all machines are patched and udpated with the newest virus definitions you should be safe. However, there are few things to be verified.
Please check these articles to eradicate this threat -
Best Practice for Downadup.B and Additional information on the same.
https://www-secure.symantec.com/connect/articles/best-practice-downadupb-and-additional-information-same
Simple steps to protect yourself from the Conficker Worm
http://service1.symantec.com/support/ent-security.nsf/docid/2009033012483648
Killing Conficker: How to Eradicate W32.Downadup for Good
https://www-secure.symantec.com/connect/articles/killing-conficker-how-eradicate-w32downadup-good
The Downadup Codex, Edition 2.0
https://www-secure.symantec.com/connect/blogs/downadup-codex-edition-20
I would also suggest you turn on the Risk Tracer to understand the source of the Risk.
What is Risk Tracer?
http://service1.symantec.com/support/ent-security.nsf/854fa02b4f5013678825731a007d06af/be1edccb0e39927280257363003a2bb3?OpenDocument
Note: Risk Tracer relies upon the Windows File and Printer Sharing. If this is disabled Risk Tracer will not work.
Also, check this Thread: https://www-secure.symantec.com/connect/forums/w32downadupb-how-could-you-find-source-if-there-are-1k-infected
Hope that helps!!