Excellent question. These types of tools pose enormous security risks, as they allow users to remotely access their PCs across the Internet using outgoing HTTP access. The tools use HTTP or HTTPS to transmit this control information, so if you allow your users to surf the Net, they can use such services. Usually, systems are protected with a user-selected password, which can often be guessed.
So, how do you block it? Sadly, because it's just HTTP, you can't just shut it off at the protocol level without stopping all Web surfing. Unfortunately, you'll have to block each Web site offering these services at a border firewall or router. Block the IP address range associated with GoToMyPC.com. Block any others you are concerned about.
Alternatively, you could use Web filtering software to block such access. The same tool you use to block porn can be used to stop access to these sites. The popular SurfControl(R) program (www.surfcontrol.com) blocks www.gotomypc.com as well as www.webex.com. Interestingly, it doesn't block www.webx.com, which takes you to the same place as www.webex.com. So, they aren't a perfect solution, but it's better than doing it all by hand with custom filters. By the way, if you want to see if a particular site is blocked by SurfControl, you can go to their www.surfcontrol.com and test to see if it is filtered by their product. Pretty cool feature!
For more information on this topic, visit these other SearchSecurity.com resources:
David Strom's Security Tool Shed: GoToMyPC a nifty utility, but can skirt security measures
Ask the Expert: Tool for monitoring correct e-mail and Internet usage
Executive Security Briefing: Where do you draw the line on employee monitoring?
This was first published in November 2002