My operating system is Windows 7 with all updates, using Windows Security Essentials and windows firewall.
For last 3 days I have been noticing popup messages from Windows Security Essentials telling me that it had prevented a trojan and than I do not need to do anything as it has taken care of it. When I checked the history tab in WSE it shows that it has quarantined Ransom:W32/Crowti or Crowti.A, there were a couple of other ones but yesterday I deleted them so cannot check their name and they haven't appeared in the log since. I don't experience any symptoms other that I have noticed the laptop sometimes feels a bit hotter and the fan revs up a bit more frequently which might suggest some process using more CPU. This might just be unrelated. When I check in the Task Manager, there is nothing abnormal with CPU usage or processes. Yesterday these WSE popups were appearing 3 times within 10 minutes and sometimes nothing for few hours. Last night I run WSE Quick scan and also Full scan overnight and also Microsoft safety scanner. Initially at the beginning of the scan WSE shows a message saying that "Preliminary results show that malicious or potencially unwanted software might be on your system, you can review detected items after scan has completed". When the scan finishes nothing shows up as detected. It gives a green tick and says Your PC is being monitored and protected. In addition to the scans i run CCleaner and Disk Cleanup and removed any temp files and any unwanted junk that windows and browsers collect. I checked for any unrecognisable apps but I haven;t noticed anything. Today WSE only quarantined Crowti only twice in the whole day.
Does the fact that WSE is preventing a trojan mean that my laptop is infected or is the trojan only trying to infect me? Is that trojan file on my system or am I being attacked from outside ie internet? Do I need to do anything or shall I leave it for WSE to keep quarantining them?