Techniques

Adversaries may abuse various implementations of JavaScript for execution. JavaScript (JS) is a platform-independent scripting language (compiled just-in-time at runtime) commonly associated with scripts in webpages, though JS can be executed in runtime environments outside the browser.[1]

JScript is the Microsoft implementation of the same scripting standard. JScript is interpreted via the Windows Script engine and thus integrated with many components of Windows such as the Component Object Model and Internet Explorer HTML Application (HTA) pages.[2][3][4]

JavaScript for Automation (JXA) is a macOS scripting language based on JavaScript, included as part of Apple’s Open Scripting Architecture (OSA), that was introduced in OSX 10.10. Apple’s OSA provides scripting capabilities to control applications, interface with the operating system, and bridge access into the rest of Apple’s internal APIs. As of OSX 10.10, OSA only supports two languages, JXA and AppleScript. Scripts can be executed via the command line utility osascript, they can be compiled into applications or script files via osacompile, and they can be compiled and executed in memory of other programs by leveraging the OSAKit Framework.[5][6][7][8][9]

Adversaries may abuse various implementations of JavaScript to execute various behaviors. Common uses include hosting malicious scripts on websites as part of a Drive-by Compromise or downloading and executing these script files as secondary payloads. Since these payloads are text-based, it is also very common for adversaries to obfuscate their content as part of Obfuscated Files or Information.

Adversaries may use junk code / dead code to obfuscate a malware’s functionality. Junk code is code that either does not execute, or if it does execute, does not change the functionality of the code. Junk code makes analysis more difficult and time-consuming, as the analyst steps through non-functional code instead of analyzing the main code. It also may hinder detections that rely on static code analysis due to the use of benign functionality, especially when combined with Compression or Software Packing.[1][2]

No-Operation (NOP) instructions are an example of dead code commonly used in x86 assembly language. They are commonly used as the 0x90 opcode. When NOPs are added to malware, the disassembler may show the NOP instructions, leading to the analyst needing to step through them.[1]

The use of junk / dead code insertion is distinct from Binary Padding because the purpose is to obfuscate the functionality of the code, rather than simply to change the malware’s signature.

Adversaries may add junk data to protocols used for command and control to make detection more difficult.[1] By adding random or meaningless data to the protocols used for command and control, adversaries can prevent trivial methods for decoding, deciphering, or otherwise analyzing the traffic. Examples may include appending/prepending data with junk characters or writing junk characters between significant characters.

Service principal names (SPNs) are used to uniquely identify each instance of a Windows service. To enable authentication, Kerberos requires that SPNs be associated with at least one service logon account (an account specifically tasked with running a service [1]). [2] [3] [4] [5]

Adversaries possessing a valid Kerberos ticket-granting ticket (TGT) may request one or more Kerberos ticket-granting service (TGS) service tickets for any SPN from a domain controller (DC). [6] [7] Portions of these tickets may be encrypted with the RC4 algorithm, meaning the Kerberos 5 TGS-REP etype 23 hash of the service account associated with the SPN is used as the private key and is thus vulnerable to offline Brute Force attacks that may expose plaintext credentials. [7] [6] [5]

This same attack could be executed using service tickets captured from network traffic. [7]

Cracked hashes may enable Persistence, Privilege Escalation, and Lateral Movement via access to Valid Accounts. [4]

Adversaries may abuse a valid Kerberos ticket-granting ticket (TGT) or sniff network traffic to obtain a ticket-granting service (TGS) ticket that may be vulnerable to Brute Force.[1][2]

Service principal names (SPNs) are used to uniquely identify each instance of a Windows service. To enable authentication, Kerberos requires that SPNs be associated with at least one service logon account (an account specifically tasked with running a service[3]).[4][5][6][7]

Adversaries possessing a valid Kerberos ticket-granting ticket (TGT) may request one or more Kerberos ticket-granting service (TGS) service tickets for any SPN from a domain controller (DC).[1][2] Portions of these tickets may be encrypted with the RC4 algorithm, meaning the Kerberos 5 TGS-REP etype 23 hash of the service account associated with the SPN is used as the private key and is thus vulnerable to offline Brute Force attacks that may expose plaintext credentials.[2][1] [7]

This same behavior could be executed using service tickets captured from network traffic.[2]

Cracked hashes may enable Persistence, Privilege Escalation, and Lateral Movement via access to Valid Accounts.[6]

Loadable Kernel Modules (or LKMs) are pieces of code that can be loaded and unloaded into the kernel upon demand. They extend the functionality of the kernel without the need to reboot the system. For example, one type of module is the device driver, which allows the kernel to access hardware connected to the system. [1] When used maliciously, Loadable Kernel Modules (LKMs) can be a type of kernel-mode Rootkit that run with the highest operating system privilege (Ring 0). [2] Adversaries can use loadable kernel modules to covertly persist on a system and evade defenses. Examples have been found in the wild and there are some open source projects. [3] [4] [5] [6]

Common features of LKM based rootkits include: hiding itself, selective hiding of files, processes and network activity, as well as log tampering, providing authenticated backdoors and enabling root access to non-privileged users. [7]

Kernel extensions, also called kext, are used for macOS to load functionality onto a system similar to LKMs for Linux. They are loaded and unloaded through kextload and kextunload commands. Several examples have been found where this can be used. [8] [9] Examples have been found in the wild. [10]

Adversaries may modify the kernel to automatically execute programs on system boot. Loadable Kernel Modules (LKMs) are pieces of code that can be loaded and unloaded into the kernel upon demand. They extend the functionality of the kernel without the need to reboot the system. For example, one type of module is the device driver, which allows the kernel to access hardware connected to the system.[1]

When used maliciously, LKMs can be a type of kernel-mode Rootkit that run with the highest operating system privilege (Ring 0).[2] Common features of LKM based rootkits include: hiding itself, selective hiding of files, processes and network activity, as well as log tampering, providing authenticated backdoors, and enabling root access to non-privileged users.[3]

Kernel extensions, also called kext, are used in macOS to load functionality onto a system similar to LKMs for Linux. Since the kernel is responsible for enforcing security and the kernel extensions run as apart of the kernel, kexts are not governed by macOS security policies. Kexts are loaded and unloaded through kextload and kextunload commands. Kexts need to be signed with a developer ID that is granted privileges by Apple allowing it to sign Kernel extensions. Developers without these privileges may still sign kexts but they will not load unless SIP is disabled. If SIP is enabled, the kext signature is verified before being added to the AuxKC.[4]

Since macOS Catalina 10.15, kernel extensions have been deprecated in favor of System Extensions. However, kexts are still allowed as "Legacy System Extensions" since there is no System Extension for Kernel Programming Interfaces.[5]

Adversaries can use LKMs and kexts to conduct Persistence and/or Privilege Escalation on a system. Examples have been found in the wild, and there are some relevant open source projects as well.[6][7][8][9][10][11][12][13]

Adversaries may abuse the KernelCallbackTable of a process to hijack its execution flow in order to run their own payloads.[1][2] The KernelCallbackTable can be found in the Process Environment Block (PEB) and is initialized to an array of graphic functions available to a GUI process once user32.dll is loaded.[3]

An adversary may hijack the execution flow of a process using the KernelCallbackTable by replacing an original callback function with a malicious payload. Modifying callback functions can be achieved in various ways involving related behaviors such as Reflective Code Loading or Process Injection into another process.

A pointer to the memory address of the KernelCallbackTable can be obtained by locating the PEB (ex: via a call to the NtQueryInformationProcess() Native API function).[4] Once the pointer is located, the KernelCallbackTable can be duplicated, and a function in the table (e.g., fnCOPYDATA) set to the address of a malicious payload (ex: via WriteProcessMemory()). The PEB is then updated with the new address of the table. Once the tampered function is invoked, the malicious payload will be triggered.[1]

The tampered function is typically invoked using a Windows message. After the process is hijacked and malicious code is executed, the KernelCallbackTable may also be restored to its original state by the rest of the malicious payload.[1] Use of the KernelCallbackTable to hijack execution flow may evade detection from security products since the execution can be masked under a legitimate process.

Adversaries may acquire credentials from Keychain. Keychain (or Keychain Services) is the macOS credential management system that stores account names, passwords, private keys, certificates, sensitive application data, payment data, and secure notes. There are three types of Keychains: Login Keychain, System Keychain, and Local Items (iCloud) Keychain. The default Keychain is the Login Keychain, which stores user passwords and information. The System Keychain stores items accessed by the operating system, such as items shared among users on a host. The Local Items (iCloud) Keychain is used for items synced with Apple’s iCloud service.

Keychains can be viewed and edited through the Keychain Access application or using the command-line utility security. Keychain files are located in ~/Library/Keychains/, /Library/Keychains/, and /Network/Library/Keychains/.[1][2][3]

Adversaries may gather user credentials from Keychain storage/memory. For example, the command security dump-keychain –d will dump all Login Keychain credentials from ~/Library/Keychains/login.keychain-db. Adversaries may also directly read Login Keychain credentials from the ~/Library/Keychains/login.keychain file. Both methods require a password, where the default password for the Login Keychain is the current user’s password to login to the macOS host.[4][5]

Keychains are the built-in way for macOS to keep track of users' passwords and credentials for many services and features such as WiFi passwords, websites, secure notes, certificates, and Kerberos. Keychain files are located in ~/Library/Keychains/,/Library/Keychains/, and /Network/Library/Keychains/. [1] The security command-line utility, which is built into macOS by default, provides a useful way to manage these credentials.

To manage their credentials, users have to use additional credentials to access their keychain. If an adversary knows the credentials for the login keychain, then they can get access to all the other credentials stored in this vault. [2] By default, the passphrase for the keychain is the user’s logon credentials.

Adversaries may collect the keychain storage data from an iOS device to acquire credentials. Keychains are the built-in way for iOS to keep track of users' passwords and credentials for many services and features such as Wi-Fi passwords, websites, secure notes, certificates, private keys, and VPN credentials.

On the device, the keychain database is stored outside of application sandboxes to prevent unauthorized access to the raw data. Standard iOS APIs allow applications access to their own keychain contained within the database. By utilizing a privilege escalation exploit or existing root access, an adversary can access the entire encrypted database.[1][2]

Adversaries may collect keychain data from an iOS device to acquire credentials. Keychains are the built-in way for iOS to keep track of users' passwords and credentials for many services and features such as Wi-Fi passwords, websites, secure notes, certificates, private keys, and VPN credentials.

On the device, the keychain database is stored outside of application sandboxes to prevent unauthorized access to the raw data. Standard iOS APIs allow applications access to their own keychain contained within the database. By utilizing a privilege escalation exploit or existing root access, adversaries can access the entire encrypted database.[1][2]

Adversaries may log user keystrokes to intercept credentials as the user types them. Keylogging is likely to be used to acquire credentials for new access opportunities when OS Credential Dumping efforts are not effective, and may require an adversary to intercept keystrokes on a system for a substantial period of time before credentials can be successfully captured. In order to increase the likelihood of capturing credentials quickly, an adversary may also perform actions such as clearing browser cookies to force users to reauthenticate to systems.[1]

Keylogging is the most prevalent type of input capture, with many different ways of intercepting keystrokes.[2] Some methods include:

* Hooking API callbacks used for processing keystrokes. Unlike Credential API Hooking, this focuses solely on API functions intended for processing keystroke data. * Reading raw keystroke data from the hardware buffer. * Windows Registry modifications. * Custom drivers. * Modify System Image may provide adversaries with hooks into the operating system of network devices to read raw keystrokes for login sessions.[3]

Adversaries may log user keystrokes to intercept credentials or other information from the user as the user types them.

Some methods of keylogging include:

* Masquerading as a legitimate third-party keyboard to record user keystrokes.[1] On both Android and iOS, users must explicitly authorize the use of third-party keyboard apps. Users should be advised to use extreme caution before granting this authorization when it is requested. * Abusing accessibility features. On Android, adversaries may abuse accessibility features to record keystrokes by registering an `AccessibilityService` class, overriding the `onAccessibilityEvent` method, and listening for the `AccessibilityEvent.TYPE_VIEW_TEXT_CHANGED` event type. The event object passed into the function will contain the data that the user typed. *Additional methods of keylogging may be possible if root access is available.

Mach-O binaries have a series of headers that are used to perform certain operations when a binary is loaded. The LC_LOAD_DYLIB header in a Mach-O binary tells macOS and OS X which dynamic libraries (dylibs) to load during execution time. These can be added ad-hoc to the compiled binary as long adjustments are made to the rest of the fields and dependencies [1]. There are tools available to perform these changes. Any changes will invalidate digital signatures on binaries because the binary is being modified. Adversaries can remediate this issue by simply removing the LC_CODE_SIGNATURE command from the binary so that the signature isn’t checked at load time [2].

Adversaries may establish persistence by executing malicious content triggered by the execution of tainted binaries. Mach-O binaries have a series of headers that are used to perform certain operations when a binary is loaded. The LC_LOAD_DYLIB header in a Mach-O binary tells macOS and OS X which dynamic libraries (dylibs) to load during execution time. These can be added ad-hoc to the compiled binary as long as adjustments are made to the rest of the fields and dependencies.[1] There are tools available to perform these changes.

Adversaries may modify Mach-O binary headers to load and execute malicious dylibs every time the binary is executed. Although any changes will invalidate digital signatures on binaries because the binary is being modified, this can be remediated by simply removing the LC_CODE_SIGNATURE command from the binary so that the signature isn’t checked at load time.[2]

**This technique has been deprecated and should no longer be used.**

As of OS X 10.8, mach-O binaries introduced a new header called LC_MAIN that points to the binary’s entry point for execution. Previously, there were two headers to achieve this same effect: LC_THREAD and LC_UNIXTHREAD [1]. The entry point for a binary can be hijacked so that initial execution flows to a malicious addition (either another section or a code cave) and then goes back to the initial entry point so that the victim doesn’t know anything was different [2]. By modifying a binary in this way, application whitelisting can be bypassed because the file name or application path is still the same.

Link-Local Multicast Name Resolution (LLMNR) and NetBIOS Name Service (NBT-NS) are Microsoft Windows components that serve as alternate methods of host identification. LLMNR is based upon the Domain Name System (DNS) format and allows hosts on the same local link to perform name resolution for other hosts. NBT-NS identifies systems on a local network by their NetBIOS name. [1] [2]

Adversaries can spoof an authoritative source for name resolution on a victim network by responding to LLMNR (UDP 5355)/NBT-NS (UDP 137) traffic as if they know the identity of the requested host, effectively poisoning the service so that the victims will communicate with the adversary controlled system. If the requested host belongs to a resource that requires identification/authentication, the username and NTLMv2 hash will then be sent to the adversary controlled system. The adversary can then collect the hash information sent over the wire through tools that monitor the ports for traffic or through Network Sniffing and crack the hashes offline through Brute Force to obtain the plaintext passwords. In some cases where an adversary has access to a system that is in the authentication path between systems or when automated scans that use credentials attempt to authenticate to an adversary controlled system, the NTLMv2 hashes can be intercepted and relayed to access and execute code against a target system. The relay step can happen in conjunction with poisoning but may also be independent of it. [3][4]

Several tools exist that can be used to poison name services within local networks such as NBNSpoof, Metasploit, and Responder. [5] [6] [7]

Adversaries may smuggle commands to download malicious payloads past content filters by hiding them within otherwise seemingly benign windows shortcut files. Windows shortcut files (.LNK) include many metadata fields, including an icon location field (also known as the `IconEnvironmentDataBlock`) designed to specify the path to an icon file that is to be displayed for the LNK file within a host directory.

Adversaries may abuse this LNK metadata to download malicious payloads. For example, adversaries have been observed using LNK files as phishing payloads to deliver malware. Once invoked (e.g., Malicious File), payloads referenced via external URLs within the LNK icon location field may be downloaded. These files may also then be invoked by Command and Scripting Interpreter/System Binary Proxy Execution arguments within the target path field of the LNK.[1][2]

LNK Icon Smuggling may also be utilized post compromise, such as malicious scripts executing an LNK on an infected host to download additional malicious payloads.

Adversaries with SYSTEM access to a host may attempt to access Local Security Authority (LSA) secrets, which can contain a variety of different credential materials, such as credentials for service accounts.[1][2][3] LSA secrets are stored in the registry at HKEY_LOCAL_MACHINE\SECURITY\Policy\Secrets. LSA secrets can also be dumped from memory.[4]

Reg can be used to extract from the Registry. Mimikatz can be used to extract secrets from memory.[4]

The Windows security subsystem is a set of components that manage and enforce the security policy for a computer or domain. The Local Security Authority (LSA) is the main component responsible for local security policy and user authentication. The LSA includes multiple dynamic link libraries (DLLs) associated with various other security functions, all of which run in the context of the LSA Subsystem Service (LSASS) lsass.exe process. [1]

Adversaries may target lsass.exe drivers to obtain execution and/or persistence. By either replacing or adding illegitimate drivers (e.g., DLL Side-Loading or DLL Search Order Hijacking), an adversary can achieve arbitrary code execution triggered by continuous LSA operations.

Adversaries may modify or add LSASS drivers to obtain persistence on compromised systems. The Windows security subsystem is a set of components that manage and enforce the security policy for a computer or domain. The Local Security Authority (LSA) is the main component responsible for local security policy and user authentication. The LSA includes multiple dynamic link libraries (DLLs) associated with various other security functions, all of which run in the context of the LSA Subsystem Service (LSASS) lsass.exe process.[1]

Adversaries may target LSASS drivers to obtain persistence. By either replacing or adding illegitimate drivers (e.g., Hijack Execution Flow), an adversary can use LSA operations to continuously execute malicious payloads.

Adversaries may attempt to access credential material stored in the process memory of the Local Security Authority Subsystem Service (LSASS). After a user logs on, the system generates and stores a variety of credential materials in LSASS process memory. These credential materials can be harvested by an administrative user or SYSTEM and used to conduct Lateral Movement using Use Alternate Authentication Material.

As well as in-memory techniques, the LSASS process memory can be dumped from the target host and analyzed on a local system.

For example, on the target host use procdump:

* procdump -ma lsass.exe lsass_dump

Locally, mimikatz can be run using:

* sekurlsa::Minidump lsassdump.dmp * sekurlsa::logonPasswords

Built-in Windows tools such as `comsvcs.dll` can also be used:

* rundll32.exe C:\Windows\System32\comsvcs.dll MiniDump PID lsass.dmp full[1][2]

Similar to Image File Execution Options Injection, the silent process exit mechanism can be abused to create a memory dump of `lsass.exe` through Windows Error Reporting (`WerFault.exe`).[3]

Windows Security Support Provider (SSP) DLLs are loaded into LSASS process at system start. Once loaded into the LSA, SSP DLLs have access to encrypted and plaintext passwords that are stored in Windows, such as any logged-on user's Domain password or smart card PINs. The SSP configuration is stored in two Registry keys: HKLM\SYSTEM\CurrentControlSet\Control\Lsa\Security Packages and HKLM\SYSTEM\CurrentControlSet\Control\Lsa\OSConfig\Security Packages. An adversary may modify these Registry keys to add new SSPs, which will be loaded the next time the system boots, or when the AddSecurityPackage Windows API function is called.[4]

The following SSPs can be used to access credentials:

* Msv: Interactive logons, batch logons, and service logons are done through the MSV authentication package. * Wdigest: The Digest Authentication protocol is designed for use with Hypertext Transfer Protocol (HTTP) and Simple Authentication Security Layer (SASL) exchanges.[5] * Kerberos: Preferred for mutual client-server domain authentication in Windows 2000 and later. * CredSSP: Provides SSO and Network Level Authentication for Remote Desktop Services.[5]

Adversaries may transfer tools or other files between systems in a compromised environment. Once brought into the victim environment (i.e., Ingress Tool Transfer) files may then be copied from one system to another to stage adversary tools or other files over the course of an operation.

Adversaries may copy files between internal victim systems to support lateral movement using inherent file sharing protocols such as file sharing over SMB/Windows Admin Shares to connected network shares or with authenticated connections via Remote Desktop Protocol.[1]

Files can also be transferred using native or otherwise present tools on the victim system, such as scp, rsync, curl, sftp, and ftp. In some cases, adversaries may be able to leverage Web Services such as Dropbox or OneDrive to copy files from one machine to another via shared, automatically synced folders.[2]

Adversaries may transfer tools or other files from one system to another to stage adversary tools or other files over the course of an operation. [1] Copying of files may also be performed laterally between internal victim systems to support Lateral Movement with remote Execution using inherent file sharing protocols such as file sharing over SMB to connected network shares. [1]

In control systems environments, malware may use SMB and other file sharing protocols to move laterally through industrial networks.