Security Task Manager is an interesting tool which analyses running processes on your PC for security threats. Any antivirus program will do much the same thing, of course, but this program doesn't use signature files, and instead relies purely on behavioural and code analysis, so may be able to pick up threats which other tools miss.
To get started with the program, just launch it and click the Windows Processes button. After a moment or two you'll see a list of all your running processes, along with their CPU and RAM use, but this time each one will have a security "rating", highlighted in red: the higher the figure, the more likely it is to be a threat.
It's important to keep in mind here that a high score doesn't necessarily mean very much. When we tried the program on a test PC, for instance, our top four highest-rated programs included Microsoft SharePoint Workspace Extensions, Windows Live ID Login Helper, and a VMware Workstation-related process, all of which were entirely safe.
Why the false alarms, then? Clicking on the SharePoint Workspace Extensions process reveals more: the process doesn't have a visible window, is able to monitor our Internet browser, has no detailed description available, records user inputs, and so on. Essentially what Security Task Manager is doing is giving each process a score for malware-like behaviour; if you're infected by malware then it may pick this up, but it'll also highlight many entirely innocent programs at the same time.
All of this means the program is a tool for initial investigations, more than anything else: your PC is behaving strangely, you think you're infected by something but your antivirus tool isn't raising any alerts, perhaps? Then run Security Task Manager, and examine its reports to see if it highlights anything which does look suspicious. And if you need to find out more, just right-click the process for options to run a Google search on the process name, or upload it to VirusTotal for a quick check by all the main antivirus tools.
Whether this is really worth the asking price of $29 is open to question, but the good news is that this is at least a one-time fee (no annual subscriptions here). And a 30-day trial is available, too, so it may be worth waiting until you're genuinely concerned about your security and need a little help. If Security Task Manager really does help to identify an infection then maybe it really does deserve a place in your long-term security toolkit.