iocextract 1.4.1

Advanced Indicator of Compromise (IOC) extractor

Advanced Indicator of Compromise (IOC) extractor.

Overview

This library extracts URLs, IP addresses, MD5/SHA hashes, and YARA rules from text corpora. It includes obfuscated and “defanged” IOCs in the output, and optionally deobfuscates them.

The Problem

It is common practice for malware analysts or endpoint software to “defang” IOCs such as URLs and IP addresses, in order to prevent accidental exposure to live malicious content. Being able to extract and aggregate these IOCs is often valuable for analysts. Unfortunately, existing “IOC extraction” tools often pass right by them, as they are not caught by standard regex.

For example, the simple defanging technique of surrounding periods with brackets:

127[.]0[.]0[.]1

Existing tools that use a simple IP address regex will ignore this IOC entirely.

The Solution

By combining specially crafted regex with some custom postprocessing, we are able to both detect and deobfuscate “defanged” IOCs. This saves time and effort for the analyst, who might otherwise have to manually find and convert IOCs into machine-readable format.

A Simple Use Case

Many Twitter users post C2s or other valuable IOC information with defanged URLs. For example, this tweet from @InQuest:

Recommended reading and great work from @unit42_intel:
https://researchcenter.paloaltonetworks.com/2018/02/unit42-sofacy-attacks-multiple-government-entities/ ...
InQuest customers have had detection for threats delivered from hotfixmsupload[.]com
since 6/3/2017 and cdnverify[.]net since 2/1/18.

If we run this through the extractor, we can easily pull out the URLs:

https://researchcenter.paloaltonetworks.com/2018/02/unit42-sofacy-attacks-multiple-government-entities/
hotfixmsupload[.]com
cdnverify[.]net

Passing in refang=True at extraction time would remove the obfuscation, but since these are real IOCs, let’s leave them defanged in our documentation. :)

Installation

Just get it from pip:

pip install iocextract

Usage

Try extracting some defanged URLs:

>>> content = """
... I really love example[.]com!
... All the bots are on hxxp://example.com/bad/url these days.
... C2: tcp://example[.]com:8989/bad
... """
>>> import iocextract
>>> for url in iocextract.extract_urls(content):
...     print url
...
hxxp://example.com/bad/url
tcp://example[.]com:8989/bad
example[.]com
tcp://example[.]com:8989/bad

Note that some URLs may show up twice if they are caught by multiple regexes.

If you want, you can also “refang”, or remove common obfuscation methods from IOCs:

>>> for url in iocextract.extract_urls(content, refang=True):
...     print url
...
http://example.com/bad/url
http://example.com:8989/bad
http://example.com
http://example.com:8989/bad

You can even extract and decode hex-encoded URLs:

>>> content = '612062756e6368206f6620776f72647320687474703a2f2f6578616d706c652e636f6d2f70617468206d6f726520776f726473'
>>> for url in iocextract.extract_urls(content):
...     print url
...
687474703a2f2f6578616d706c652e636f6d2f70617468
>>> for url in iocextract.extract_urls(content, refang=True):
...     print url
...
http://example.com/path

All extract_* functions in this library return iterators, not lists. The benefit of this behavior is that iocextract can process extremely large inputs, with a very low overhead. However, if for some reason you need to iterate over the IOCs more than once, you will have to save the results as a list:

>>> list(iocextract.extract_urls(content))
['hxxp://example.com/bad/url', 'tcp://example[.]com:8989/bad', 'example[.]com', 'tcp://example[.]com:8989/bad']

A command-line tool is also included:

$ iocextract -h
usage: iocextract [-h] [--input INPUT] [--output OUTPUT] [--extract-ips]
                  [--extract-urls] [--extract-yara-rules] [--extract-hashes]
                  [--refang] [--strip-urls]

Advanced Indicator of Compromise (IOC) extractor. If no arguments are
specified, the default behavior is to extract all IOCs.

optional arguments:
  -h, --help            show this help message and exit
  --input INPUT         default: stdin
  --output OUTPUT       default: stdout
  --extract-ips
  --extract-urls
  --extract-yara-rules
  --extract-hashes
  --refang              default: no
  --strip-urls          remove possible garbage from the end of urls. default:
                        no
  --wide                preprocess input to allow wide-encoded character
                        matches. default: no

Only URLs and IPv4 addresses can be “refanged”.

More Details

This library currently supports the following IOCs:

• IP Addresses

  • IPv4 fully supported

  • IPv6 partially supported

• URLs

  • With protocol specifier: http, https, tcp, udp, ftp, sftp, ftps

  • With [.] anchor, even with no protocol specifier

  • IPv4 and IPv6 (RFC2732) URLs are supported

  • Hex-encoded URLs with protocol specifier: http, https, ftp

  • URL-encoded URLs with protocol specifier: http, https, ftp, ftps, sftp

• Emails

  • Partially supported, anchoring on @

• YARA rules

• Hashes

  • MD5

  • SHA1

  • SHA256

  • SHA512

For IPv4 addresses, the following defang techniques are supported:

Technique	Defanged	Refanged
. -> [.]	1[.]1[.]1[.]1	1.1.1.1
. -> (.)	1(.)1(.)1(.)1	1.1.1.1
. -> \.	1\.1\.1\.1	1.1.1.1
Partial	1[.1[.1.]1	1.1.1.1
Any combination	1.)1[.1.)1	1.1.1.1

For URLs, the following defang techniques are supported:

Technique	Defanged	Refanged
. -> [.]	example[.]com/path	http://example.com/path
. -> (.)	example(.)com/path	http://example.com/path
. -> \.	example\.com/path	http://example.com/path
Partial	http://example[.com/path	http://example.com/path
/ -> [/]	http://example.com[/]path	http://example.com/path
Cisco ESA	http:// example .com /path	http://example.com/path
:// -> __	http__example.com/path	http://example.com/path
hxxp	hxxp://example.com/path	http://example.com/path
Any combination	hxxp__ example( .com[/]path	http://example.com/path
Hex encoded	687474703a2f2f6578616d706c652e636f6d2f70617468	http://example.com/path
URL encoded	http%3A%2F%2fexample%2Ecom%2Fpath	http://example.com/path

Note that the table above is not exhaustive, and other URL/defang patterns may also be extracted correctly. If you notice something missing or not working correctly, feel free to let us know via the GitHub Issues.

Changelog

New features, improvements, and bugfixes for each release can be found in the GitHub releases.

Contributing

If you have a defang technique that doesn’t make it through the extractor, or if you find any bugs, PRs and Issues are always welcome. The library is released under a “BSD-New” (aka “BSD 3-Clause”) license.