According to jail.conf we actually need to separate multiple values
with spaces instead of commas. On some versions of fail2ban this is
a fatal error:
> CRITICAL Unhandled exception in Fail2Ban:
> Traceback (most recent call last):
> File "/usr/lib/python3/dist-packages/fail2ban/server/jailthread.py", line 66, in run_with_except_hook
> run(*args, **kwargs)
> File "/usr/lib/python3/dist-packages/fail2ban/server/filtersystemd.py", line 246, in run
> *self.formatJournalEntry(logentry))
> File "/usr/lib/python3/dist-packages/fail2ban/server/filter.py", line 432, in processLineAndAdd
> if self.inIgnoreIPList(ip, log_ignore=True):
> File "/usr/lib/python3/dist-packages/fail2ban/server/filter.py", line 371, in inIgnoreIPList
> "(?<=b)1+", bin(DNSUtils.addr2bin(s[1]))).group())
> File "/usr/lib/python3/dist-packages/fail2ban/server/filter.py", line 928, in addr2bin
> return struct.unpack("!L", socket.inet_aton(ipstring))[0]
> OSError: illegal IP address string passed to inet_aton
This affects (at least) fail2ban 0.9.3 on Ubuntu 16.04, but I never
noticed.