Q All of a sudden, I have noticed a new icon in the sidebar of my iMac’s Finder windows, in the Shared section, named ep3f30ee and claiming to be a PC server. Where did this server come from?
A Unless you need to use AirPort on your iMac for its network connection, try turning it off in the Network pane. Most devices that appear in this way are stray wireless connections that could simply be unintended, or may even be malicious.
If it disappears when AirPort is off, then you know how it is connecting; next you need to identify what and where it is. One interesting possibility is that you (or a close neighbour) has recently installed a printer that supports wireless connections, possibly using Bonjour; as its name starts with ‘ep’, it is possible that it is an Epson printer or all-in-one.
Other suggestions include a neighbour’s PC, which could be offering itself up in this way, or even someone deliberately accessing your wireless network (or you accessing someone else’s). Any of these make it very important that you revisit your wireless network settings and ensure that they are secure and do not allow such intrusion. Further advice on wireless security is here.
Updated from the original, which was first published in MacUser volume 26 issue 7, 2010.