Looking down my ACP login attempts list there is a huge number of attempts may by people apparently trying to get in, with generic usernames, etc.

No enough to be what I would call a brute-force attack or anything like that, but just surprised me and and wondered if it was something to worry about?

Daniel

Look Here:

http://community.invisionpower.com/topic/386787-hacking-attempt-best-practices-for-blocking-this/

http://community.invisionpower.com/topic/387503-multiple-admincp-login-attempts/

That's either a very poor attempt at "hacking" into your ACP, or a badly coded crawler. Either way, annoying.

We'd suggest blocking two ranges in your server Firewall. They're owned by the same entity and smell suspicious:

37.1.200.0/21

5.45.64.0/21

Those ranges have been the two we've seen being used so far.