S0061 FoggyWeb

FoggyWeb is a passive and highly-targeted backdoor capable of remotely exfiltrating sensitive information from a compromised Active Directory Federated Services (AD FS) server. It has been used by APT29 since at least early April 2021.[1].

FoggyWebは、感染したActive Directory Federated Services(AD FS)サーバから機密情報をリモートで盗み出すことができる、受動的で高度な標的型バックドアです。少なくとも2021年4月初旬以降、APT29によって使用されています。(passiveについては、[1]を参照)

Platforms: Windows
Contributors: Craig Smith, BT Security
Version: 1.0
Created: 16 November 2021
原文:Last Modified: 15 April 2022

Techniques Used

Domain ID Name Use
Enterprise T1071 .001 Application Layer Protocol: Web Protocols

FoggyWeb has the ability to communicate with C2 servers over HTTP GET/POST requests.[1]

Enterprise T1560 .002 Archive Collected Data: Archive via Library

FoggyWeb can invoke the Common.Compress method to compress data with the C# GZipStream compression class.[1]

    .003 Archive Collected Data: Archive via Custom Method

FoggyWeb can use a dynamic XOR key and a custom XOR methodology to encode data before exfiltration. Also, FoggyWeb can encode C2 command output within a legitimate WebP file.[1]

Enterprise T1005 Data from Local System

FoggyWeb can retrieve configuration data from a compromised AD FS server.[1]

Enterprise T1140 Deobfuscate/Decode Files or Information

FoggyWeb can be decrypted in memory using a Lightweight Encryption Algorithm (LEA)-128 key and decoded using a XOR key.[1]

Enterprise T1573 .001 Encrypted Channel: Symmetric Cryptography

FoggyWeb has used a dynamic XOR key and custom XOR methodology for C2 communications.[1]

Enterprise T1041 Exfiltration Over C2 Channel

FoggyWeb can remotely exfiltrate sensitive information from a compromised AD FS server.[1]

Enterprise T1083 File and Directory Discovery

FoggyWeb's loader can check for the FoggyWeb backdoor .pri file on a compromised AD FS server.[1]

Enterprise T1574 .001 Hijack Execution Flow: DLL Search Order Hijacking

FoggyWeb's loader has used DLL Search Order Hijacking to load malicious code instead of the legitimate version.dll during the Microsoft.IdentityServer.ServiceHost.exe execution process.[1]

Enterprise T1105 Ingress Tool Transfer

FoggyWeb can receive additional malicious components from an actor controlled C2 server and execute them on a compromised AD FS server.[1]

Enterprise T1036 Masquerading

FoggyWeb can masquerade the output of C2 commands as a fake, but legitimately formatted WebP file.[1]

    .005 Match Legitimate Name or Location

FoggyWeb can be disguised as a Visual Studio file such as Windows.Data.TimeZones.zh-PH.pri to evade detection. Also, FoggyWeb's loader can mimic a genuine dll file that carries out the same import functions as the legitimate Windows version.dll file.[1]

Enterprise T1106 Native API

FoggyWeb's loader can use API functions to load the FoggyWeb backdoor into the same Application Domain within which the legitimate AD FS managed code is executed.[1]

Enterprise T1040 Network Sniffing

FoggyWeb can configure custom listeners to passively monitor all incoming HTTP GET and POST requests sent to the AD FS server from the intranet/internet and intercept HTTP requests that match the custom URI patterns defined by the actor.[1]

Enterprise T1027 Obfuscated Files or Information

FoggyWeb has been XOR-encoded.[1]

    .004 Compile After Delivery

FoggyWeb can compile and execute source code sent to the compromised AD FS server via a specific HTTP POST.[1]

Enterprise T1057 Process Discovery

FoggyWeb's loader can enumerate all Common Language Runtimes (CLRs) and running Application Domains in the compromised AD FS server's Microsoft.IdentityServer.ServiceHost.exe process.[1]

Enterprise T1620 Reflective Code Loading

FoggyWeb's loader has reflectively loaded .NET-based assembly/payloads into memory.[1]

Enterprise T1129 Shared Modules

FoggyWeb's loader can call the load() function to load the FoggyWeb dll into an Application Domain on a compromised AD FS server.[1]

Enterprise T1552 .004 Unsecured Credentials: Private Keys

FoggyWeb can retrieve token signing certificates and token decryption certificates from a compromised AD FS server.[1]

Enterprise T1550 Use Alternate Authentication Material

FoggyWeb can allow abuse of a compromised AD FS server's SAML token.[1]

Groups That Use This Software

ID Name References
G0016 APT29