List networks related to a given AS number, or IP address.
In theory, you should be able to watch for regular expressions in your webserver
(or whatever) logs, grep suspicious ones, pipe them to asls, then either add
rules to your firewall, or directives to your webserver configuration, ...
In practice, give it a try:
syn@toto:~$ asls 82.237.197.108/24
62.147.0.0/16
78.192.0.0/10
81.56.0.0/15
82.64.0.0/14
82.142.0.0/18
82.224.0.0/11
83.152.0.0/13
83.214.0.0/16
88.120.0.0/13
88.160.0.0/11
91.160.0.0/12
212.27.32.0/19
213.36.0.0/16
213.228.0.0/18