Learning Aid - Top Base64 Encodings Table

Base64_CheatSheet.md

Base64 Patterns - Learning Aid

Base64 Code	Mnemonic Aid	Decoded*	Description
JAB	🗣 Jabber	$.	Variable declaration (UTF-16), e.g. JABlAG4AdgA for $env:
TVq	📺 Television	MZ	MZ header
SUVY	🚙 SUV	IEX	PowerShell Invoke Expression
SQBFAF	🐣 Squab favorite	I.E.	PowerShell Invoke Expression (UTF-16)
SQBuAH	🐣 Squab uahhh	I.n.	PowerShell Invoke string (UTF-16) e.g. Invoke-Mimikatz
PAA	💪 "Pah!"	<.	Often used by Emotet (UTF-16)
cwBhA	🦁 Chewbaka	s.a.	Often used in malicious droppers (UTF-16) 'sal' instead of 'var'
aWV4	😲 Awe version 4	iex	PowerShell Invoke Expression
aQBlA	💦 Aqua Blah (aquaplaning)	i.e.	PowerShell Invoke Expression (UTF-16)
R2V0	🤖 R2D2 but version 0	Get	Often used to obfuscate imports like GetCurrentThreadId
dmFy	👹 defy / demonify	var	Variable declaration
dgBhA	debugger + high availability	v.a.	Variable declaration (UTF-16)
dXNpbm	Dixon problem	usin	Often found in compile after delivery attacks
H4sIA	🚁 HForce (Helicopter Force) I agree		gzip magic bytes (0x1f8b), e.g. echo 'test' | gzip -cf | base64
Y21k	🎆 Year 21k bug	cmd	As used in cmd.exe /c wscript.exe or the like
IAB	🥱 I am bored	s	wide lower case s, often something like sEt-iTem
cABhAH	🕋 Kaaba	p.a.	wide formatted param
Qzpc	🖥 Quiz PC	C:\	Root of Windows partition (upper case)
Yzpc	🖥 Yes PC	c:\	Root of Windows partition (lower case)
UEs	🏬 Upper East Side	PK	ZIP, Office documents
ey	🗣 Hey	{	Indicates JSON data

* the . stands for 0x00 found in UTF-16 encoded text

Often found patterns

Base64 Code	Decoded	Description
AAAAAAAAAAAA	\x00\x00\x00\x00\x00\x00\x00\x00\x00	Sequence of binary zeros
////////////	\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF	Sequence of 0xFF bytes
ICAgICAgICAg		Sequence of space characters

Cyber Chef Recipe

https://gchq.github.io/CyberChef/#recipe=Fork('%5C%5Cn','%5C%5Cn',false)From_Base64('A-Za-z0-9%2B/%3D',true)&input=SkFCClRWcQpQQUEKU1VWWQpTUUJGQUYKYVdWNAphUUJsQQpSMlYwCmRtRnkKZGdCaEEKY3dCaEEKZFhOcGJtCkg0c0lBRldXc2wwQUF5dEpMUzdoQWdER05iazdCUUFBQUE9PQ

References

Tweet

Tweet and Thread https://twitter.com/cyb3rops/status/1187341941794660354

JAB

https://www.hybrid-analysis.com/sample/ce0415b6661ef66bbedb69896ad1ece9ee4e6dfde9925e9612aec7bbf1cb7bc5?environmentId=100

PAA

Emotet process command line https://app.any.run/tasks/dfba6d53-7a93-4d8b-86ba-4e737ad06b06/

cwBha

Explanation https://threat.tevora.com/5-minute-forensics-decoding-powershell-payloads/

Sample https://www.hybrid-analysis.com/sample/b744129bfe54de8b36d7556ddfcc55d0be213129041aacf52b7d2f57012caa60?environmentId=100

Please mention that these encodings only hold at the start of the encoded string and will not work consistently at other positions. Most people aren't aware of the 3 byte chunks used to encode base64 and the 3 encodings repetition you get by shifting one byte at a time. Also IAB decodes to 0x20 0x00 not 0x73 0x00.
Here's an example of determining the consistent subset of an encoded string at the 3 offsets. (wide "s" used) https://gchq.github.io/CyberChef/#recipe=Fork('%5C%5Cn','%5C%5Cn',false)From_Hex('Auto')To_Base64('A-Za-z0-9%2B/%3D')&input=NzMgMDAgMDAgMDAKNzMgMDAgNzcgNzcKNzMgMDAgRkYgRkYKMDAgNzMgMDAgMDAgMDAKNzcgNzMgMDAgNzcgNzcKRkYgNzMgMDAgRkYgRkYKMDAgMDAgNzMgMDAgMDAgMDAgMDAKNzcgNzcgNzMgMDAgNzcgNzcgNzcKRkYgRkYgNzMgMDAgRkYgRkYgRkYKMDAgMDAgMDAgNzMgMDAgMDAgMDAgMDAKNzcgNzcgNzcgNzMgMDAgNzcgNzcgNzcKRkYgRkYgRkYgNzMgMDAgRkYgRkYgRkYKMDAgMDAgMDAgMDAgNzMgMDAgMDAgMDAgMDAKNzcgNzcgNzcgNzcgNzMgMDAgNzcgNzcgNzcKRkZGRiBGRiBGRiA3MyAwMCBGRiBGRiBGRgoK
Unless you're only checking the start of a buffer you'll need to trim a bit off the front and back to safely detect the consistent substring of what you're looking for. From the example of wide "s" you have cw, MA, zA. I added extra shifts in Cyberchef to illustrate the cycle and how the pattern comes back every 3rd byte.

Very cool gist! It occured to me: ey misses a quote after the brace: {". And any idea for aHR0cHM6Ly8= (https://)?

This is amazing btw.