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routinely I'm seeing lots of login attempts to my mail server trying out various login names starting from A to Z coming from the one IP on one day and another IP on another day. Is there any means to detect this type of activities and block accordingly? I asked Watchguard and it appears they don't support this on their XTM series. Anything else I can do other than to have a super long password?

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Are the IP addresses in the same subnet ? Can you limit the number of login attempts ? – Vinz Nov 5 '13 at 15:17
@Vinz No it comes from a variety of IPs. – user192702 Nov 10 '13 at 12:46

This is a typical example of the "background noise" you'll find on most servers exposed to the internet.

A common solution is to have a script parse your log files to find those repeat offenders and then block the originating ip-adresses in the servers local firewall.

fail2ban is one such example.

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Is there a way to block it on the network device level with any UTM devices? I'd tend to think the XTM series would do such thing but apparently not. – user192702 Nov 10 '13 at 12:47
I have no experience with Watchguard products, so I can't help you there. I imagine it also strongly depends on the protocol, a clear text protocol would allow an intrusion detection/prevention appliance easily tally incorrect username/password messages and take action. If the protocol/connection is SSL/TLS encrypted the appliance would need a copy of the private key and actively decrypt all traffic, which I would expect to come at an performance and price premium. Depending on the number and skill level of your legitimate users you could move services to non-default ports. – HBruijn Nov 10 '13 at 19:37

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