Alarmed by port 445

Reader Steve Good believes that his Mac is up to no good. He writes:

Every few minutes my Power Mac G4 (running Panther) tries to communicate with the other Macs and PCs on my home network. The communications come from port 445 and systematically try ports above 49000. I have no idea about the cause. Is malware probing my computers for an unguarded way in? How do I evict it?

It’s not malware. In fact, this behavior is caused by something you’ve initiated.

Port 445 is used for SMB (or Server Message Block , a networking protocol used by Windows, and now the Mac, for sharing files). If you’ve switched on Windows Sharing in the Sharing system preference, your Mac will occasionally nudge your Windows PC to make sure the two are still on speaking terms. This nudge is what’s setting off the alarms on your PC. If you’d like to put an end to them—and you’re not sharing files between the two machines—simply switch off Windows Sharing.

If you are sharing files and a program such as Zone Labs’ ZoneAlarm continues to spit up a warning every time the Mac touches the PC, configure the alarmed utility so it accepts your Mac as a trusted member of your network (IOW, tell it that any request from your Mac’s IP address should be accepted without question).

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