I’ve been wrestling with Fierce domain scanner for several months now, and upgrade it at least once every few weeks. Thanks to WhiteAcid who got me in touch with IceShaman we have now ported it to use multi-threading options. This is especially useful if you have PERL compiled with the useithreads option compiled into it. That can drastically reduce the time it takes to perform a scan, especially on a large domain. Oh, but that’s not all, I’ve heard a few complaints about not being able to use multiple DNS servers when you are doing lookups (this reduces the noise of a scan as it spreads it out to many DNS servers with the -dnsfile switch).
Fierce also now just assumes you want to use hosts.txt unless you otherwise state so. That can help when you are trying to quickly perform the scan. To take advantage of these new switches, try something like this:
perl fierce.pl -dns testdomain.com -wide -file output.txt -dnsfile dnsfile.txt -threads 40
The -wide switch makes Fierce search the entire class C for any matches - note that it sometimes errors with a deep recursion if it finds a lot of hosts on a single class C, but this doesn’t affect its functionality. It can slow it down around 51x (255/5) but it can also find a lot more hosts than without. Compare rambler.ru old default scan with rambler.ru new scan with -wide switch.
I’ve also fixed the issue with dumping the zone transfers. Now it will query each and every DNS server (primary, secondary and otherwise) and see if they can get zone transfers from each of them. That can drastically speed up the scan now that it works, and also fixes a bug where it would intermittently work (when one DNS server could transfer the zone and another one won’t - that was a frustrating bug fix). There has been a few minor other enhancements since the last time I posted about Fierce, not the least of which is a far better hosts.txt file that does a much better job of locating larger swaths of networks. Hopefully that will quell a lot of people’s feelings about what Fierce was lacking. So a huge thanks to IceShaman for doing a bulk of the changes, and look for more improvements in the future.