Malleable-C2-Randomizer

This script randomizes Cobalt Strike Malleable C2 profiles through the use of a metalanguage, hopefully reducing the chances of flagging signature-based detection controls. In short, the script parses the provided template, substitutes the variables for a random value from either a provided or built-in wordlist, tests the new template with c2lint, and (if there are no c2lint errors) outputs the new Malleable C2 profile.

Sample Malleable C2 profiles that are compatible with this script can be found in the Sample Templates directory of this repo.

For more about this script, check out my blog post Randomized Malleable C2 Profiles Made Easy.

Table of Contents

• Script Syntax
  • Basic Options
  • Custom Wordlists
• Substitution Metalanguage
  • List of Variables
  • Building Wordlists
• Example Template and Output
• Further Resources

Script Syntax

python malleable-c2-randomizer.py [-h] -profile PROFILE
                                  [-count COUNT]
                                  [-cobalt COBALT]
                                  [-output OUTPUT]
                                  [-notest]
                                  [-charset CHARSET]
                                  [-wordlist WORDLIST]
                                  [-useragent USERAGENT]
                                  [-spawnto SPAWNTO]
                                  [-pipename PIPENAME]
                                  [-pipename_stager PIPENAME_STAGER]
                                  [-dns_stager_subhost DNS_STAGER_SUBHOST]

Basic Options

Custom Wordlists

If no wordlist is provided, a built-in list will be used by default. For more information about creating these lists, see below or the Sample Wordlists folder in this repo.

Most of these wordlist variables are directly related to Malleable C2 options. For more information about what these profile options do, check out the official documentation.

Substitution Metalanguage

The substitution metalanguage comprises specific variables, some of which allow optional repetition counts, wrapped in double percentage signs, like so:

%%variable:count%%

As another example, the following variable will result in 20 alphanumeric characters:

%%alphanumeric:20%%

List of Variables

Building Wordlists

Wordlist files are simply line-separated, tab-separated, or continuous strings (depending on the wordlist type) place in a text file.

The following wordlists should be line-separated with each entry on a new line:

• wordlist
• useragent
• pipename
• pipename_stager
• dns_stager_subhost
• dns_stager_prepend

The spawnto wordlist is a bit more complicated. Malleable C2 requires an x86 and x64 option to modify all process spawning. Therefore, each line of the wordlist should contain both the x86 and x64 process paths separated by a tab, with the x86 process listed first. For example:

%windir%\\syswow64\\eventvwr.exe	%windir%\\sysnative\\eventvwr.exe

It's important to note that the syswow64 and sysnative strings in the process paths should be lowercase.

The final wordlist type is the custom characterset. This file should include any characters for the script to randomly substitute. For example, a charset file of AEIOUY and a variable of %%custom:5%% will output five random characters from the charset string. When building this characterset, bear in mind that some characters are prohibited from appearing in a URI and may interfere with Beacon's communications.

For sample wordlists, see the Sample Wordlists directory in this repo.

Example Template and Output

Here is a snippet from a modified Amazon profile:

# This profile has been modified to use with the Malleable C2 Profile Randomizer

#
# Amazon browsing traffic profile
# 
# Author: @harmj0y
#

set sleeptime "%%number:2%%00";
set jitter    "1%%number%%";
set maxdns    "24%%number%%";
set useragent "%%useragent%%";

http-get {

    set uri "/s/ref=nb_sb_noss_1/%%number:3%%-%%number:8%%-%%number:7%%/field-keywords=%%word%%";

    client {

        header "Accept" "*/*";
        header "Host" "www.amazon.com";

        metadata {
            base64;
            prepend "session-token=";
            prepend "skin=noskin;";
            append "csm-hit=s-%%alphanumeric:20%%|%%number:13%%";
            header "Cookie";
        }
    }
}

And here is two sets of output from the same profile:

# This profile has been modified to use with the Malleable C2 Profile Randomizer

#
# Amazon browsing traffic profile
# 
# Author: @harmj0y
#

set sleeptime "5600";
set jitter    "19";
set maxdns    "244";
set useragent "Mozilla/5.0 (Windows NT 6.1; WOW64; rv:40.0) Gecko/20100101 Firefox/40.1";

http-get {

    set uri "/s/ref=nb_sb_noss_1/818-61846941-6716865/field-keywords=number";

    client {

        header "Accept" "*/*";
        header "Host" "www.amazon.com";

        metadata {
            base64;
            prepend "session-token=";
            prepend "skin=noskin;";
            append "csm-hit=s-UXnlEVYWc36qEuDMFPzW|2872195700726";
            header "Cookie";
        }
    }
}

# This profile has been modified to use with the Malleable C2 Profile Randomizer

#
# Amazon browsing traffic profile
# 
# Author: @harmj0y
#

set sleeptime "7400";
set jitter    "19";
set maxdns    "246";
set useragent "Mozilla/5.0 (Windows NT 10.0; WOW64)";

http-get {

    set uri "/s/ref=nb_sb_noss_1/684-10075672-1686806/field-keywords=year";

    client {

        header "Accept" "*/*";
        header "Host" "www.amazon.com";

        metadata {
            base64;
            prepend "session-token=";
            prepend "skin=noskin;";
            append "csm-hit=s-ub5oBmGd0pnDoImCjDyK|2539750656854";
            header "Cookie";
        }
    }
}

Further Resources

• Randomized Malleable C2 Profiles Made Easy - Jeff Dimmock
• Malleable Command and Control Documentation - Raphael Mudge
• Malleable C2 Profiles - GitHub
• How to Write Malleable C2 Profiles for Cobalt Strike - Jeff Dimmock
• Cobalt Strike 2.0 - Malleable Command and Control - Raphael Mudge
• Cobalt Strike 3.6 - A Path for Privilege Escalation - Raphael Mudge
• A Brave New World: Malleable C2 - Will Schroeder