On Thursday morning, IT consultant Paul Nash received an urgent call from a client whose Apache webserver had crashed the previous night and inexplicably wouldn't restart. Equally vexing, people who tried to visit the client's website during the 10-hour outage received a message advertising TeamViewer, a maker of widely used software for remotely managing PCs and servers.

After 90 minutes of troubleshooting, Nash traced the problem to TeamViewer, which he used to remotely administer the client's servers. It turns out the program had opened up its own webserver on the client's machine as soon as Apache went down and in the process made it impossible for the client, a large provider of business software, to restart its proper website.

"At that point, basically the webserver is hosed because if Apache tries to start up again, it sees someone else on port 80 and it falls over and dies, which is kind of antisocial behavior," Nash, who is the principal at Toronto-based Nash Networks, told The Register. Nash was able to get Apache up and running again by killing TeamViewer processes on the server, but by then, the client "had quite a bit of irate support requests stacked up."

The incident highlights a serious liability that comes from using what he otherwise regards as a great tool for remotely managing the thousands of PCs and servers entrusted to him. But what really sticks in Nash's craw, he said, is the blase attitude TeamViewer support people showed when he reported the SNAFU.

"They said they don't see what the problem is," he said.

After he escalated the complaint, Nash finally received instructions for modifying the registry of machines running TeamViewer so its webserver won't automatically start should the normal webserver go down. But this requires him to put his hands on every machine he manages, a solution that's needlessly cumbersome.

Also concerning, said Nash, is TeamViewer's lack of disclosure that its software is receiving incoming traffic sent to machines that run the software.

"They're sitting in the middle and they're in a position to snoop on all my traffic," he said, adding that he thinks that scenario is unlikely. Still, when Nash learned that TeamViewer does monitor for incoming web requests, he said it made him wonder: "What else aren't they telling us?"

TeamViewer's website claims the software has more than 15 million installations in 50 countries. Company representatives didn't immediately respond to requests for comment sent early Friday evening Germany time. We'll be sure to update this article, if they get back to us. ®

Update

A TeamViewer representative emailed us the following:

Yes TeamViewer tries to use port 80 if available first. TeamViewer also waits about 10 Minutes for an eventually available Webserver to start. If this doesn't happen because there is no Webserver or because the Webserver crashes TeamViewer grabs port 80. If you should start the Webserver afterwards TeamViewer still uses port 80 so the Webserver can't work on it. If you then close TeamViewer or restart the PC you can reallocate port 80 again.