Not sure why you have posted this on the Norton Mobile Security forum but I note that the Android Market says the following about "Android Market Security Tool"
This is an Android Market security update that undoes exploits caused by the malicious applications that were removed from Android Market on 03/01/2011. Only some users were affected. Those users will receive an email notification that states this update will be automatically pushed to their devices. This app will be removed automatically after it has completed running.
You are NOT required to take any action whatsoever to undo the exploit on your device. For more information, visit http://goo.gl/P8Iqk.
So it looks as if Android thinks you have had a malicious infection but I'm not sure why it is still there. Do you regularly connect to the Market? If not you might like to connect and see if it goes away after that.
If you are experiencing an issue that needs urgent assistance please visit our customer support area:
There are currently 4 users online.