Quick hack to reverse a list of IPs to their hostnames from firewall logs, this assumes python 2.7/3 and pandas are available

unravel.py

#!/bin/env python

import pandas as pd
import socket

df = pd.read_csv('<sourcecsv>.csv')
ips=df["Source address"]
for ip in ips:
  print (socket.gethostbyaddr(str(ip)))