FTP brute password guessing attacks are a fairly regular occurrence at the moment. The fact that these are occurring with regularity means that they are still working, so If you have an internet facing FTP server then there are a few things that you might consider doing to help weather the storm. Watch your logs!
09:19:44 211.45.113.143 [2]USER Administrator 331 0
It is quite clear what is going on here. a user typing a password multiple times per second? not likely. The log shows very clearly what is going on someone is guessing passwords. In this case it was a Microsoft FTP server which was being attacked, so there is likely to be an administrator account on the system and eventually this attack result in access. Many people don't have their logging enabled. Make sure it is switched on and watched regularly, this is something junior can do on his own. Rename Administrator Remove Anonymous Access Restrict Access to FTP The above are a few simple ways to reduce the risk of losing your FTP server to someone else. If you have some nifty tricks that will help protect an FTP service, write a comment or use the contact form. Cheers
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Mark 392 Posts ISC Handler Aug 27th 2010 |
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Aug 27th 2010 1 decade ago |
I would suggest perform having a strong password policy in place and performing passwords audits against said policy. This also includes checking for weak passwords (dictionary words) that may still meet policy requirements, but is easily guessable.
You can also use cewl (http://www.digininja.org/projects/cewl.php) or userpass (http://pauldotcom.com/2010/08/draft---creating-per-user-cust.html) to generate a dictionary that is relevant to an organization. I have given Ron Bowes a list of passwords that were collected from a Honeynet that I run. These passwords were largely collected from FTP password guessing attacks. (http://www.skullsecurity.org/wiki/index.php/Passwords) |
Anonymous |
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Aug 27th 2010 1 decade ago |
On my public facing FTP server, I have a few scripts setup to automatically ban/block these IPs that are trying brute force attacks, as well as other scripts to automatically disable stale FTP accounts and remove old data. Seems to be working pretty well so far. My list of banned IPs is growing nicely, and no legitimate FTP users have been affected yet (but we have very few, mainly a few vendors/contractors and only for short periods of time.)
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Shawn 29 Posts |
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Aug 27th 2010 1 decade ago |
If you absolutely must have FTP, and you absolutely must have it open to varying IP addresses, then you should consider tools like fail2ban that will block an IP after it exceeds a failed login threshold.
If at all possible, look into moving to SFTP, FTPS or even WebDAV over SSL. With any of these, you can even employ client certificates and permanently disable password-only authentication. With any solution, you should still employ the other relevant advice here and make sure the configuration is sound (authentication and authorization, quotas, access and permissions, etc.) and test that everything works [only] as intended. |
Shawn 11 Posts |
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Aug 29th 2010 1 decade ago |
With some of my BSD boxen, what I will do is create nologin accts for these often attacked users (admin, administrator) and they add them to /etc/ftpusers - that way they get an outright denial just from sending the user name
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Chavez243 15 Posts |
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Aug 30th 2010 1 decade ago |
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