Techniques

Adversaries may attempt to dump the contents of /etc/passwd and /etc/shadow to enable offline password cracking. Most modern Linux operating systems use a combination of /etc/passwd and /etc/shadow to store user account information, including password hashes in /etc/shadow. By default, /etc/shadow is only readable by the root user.[1]

Linux stores user information such as user ID, group ID, home directory path, and login shell in /etc/passwd. A "user" on the system may belong to a person or a service. All password hashes are stored in /etc/shadow - including entries for users with no passwords and users with locked or disabled accounts.[1]

Adversaries may attempt to read or dump the /etc/passwd and /etc/shadow files on Linux systems via command line utilities such as the cat command.[2] Additionally, the Linux utility unshadow can be used to combine the two files in a format suited for password cracking utilities such as John the Ripper - for example, via the command /usr/bin/unshadow /etc/passwd /etc/shadow > /tmp/crack.password.db[3]. Since the user information stored in /etc/passwd are linked to the password hashes in /etc/shadow, an adversary would need to have access to both.

Adversaries may interrupt availability of system and network resources by inhibiting access to accounts utilized by legitimate users. Accounts may be deleted, locked, or manipulated (ex: changed credentials, revoked permissions for SaaS platforms such as Sharepoint) to remove access to accounts.[1] Adversaries may also subsequently log off and/or perform a System Shutdown/Reboot to set malicious changes into place.[2][3]

In Windows, Net utility, Set-LocalUser and Set-ADAccountPassword PowerShell cmdlets may be used by adversaries to modify user accounts. Accounts could also be disabled by Group Policy. In Linux, the passwd utility may be used to change passwords. On ESXi servers, accounts can be removed or modified via esxcli (`system account set`, `system account remove`).

Adversaries who use ransomware or similar attacks may first perform this and other Impact behaviors, such as Data Destruction and Defacement, in order to impede incident response/recovery before completing the Data Encrypted for Impact objective.

Adversaries may manipulate accounts to maintain and/or elevate access to victim systems. Account manipulation may consist of any action that preserves or modifies adversary access to a compromised account, such as modifying credentials or permission groups.[1] These actions could also include account activity designed to subvert security policies, such as performing iterative password updates to bypass password duration policies and preserve the life of compromised credentials.

In order to create or manipulate accounts, the adversary must already have sufficient permissions on systems or the domain. However, account manipulation may also lead to privilege escalation where modifications grant access to additional roles, permissions, or higher-privileged Valid Accounts.

Adversaries may purchase or otherwise acquire an existing access to a target system or network. A variety of online services and initial access broker networks are available to sell access to previously compromised systems.[1][2][3] In some cases, adversary groups may form partnerships to share compromised systems with each other.[4]

Footholds to compromised systems may take a variety of forms, such as access to planted backdoors (e.g., Web Shell) or established access via External Remote Services. In some cases, access brokers will implant compromised systems with a “load” that can be used to install additional malware for paying customers.[1]

By leveraging existing access broker networks rather than developing or obtaining their own initial access capabilities, an adversary can potentially reduce the resources required to gain a foothold on a target network and focus their efforts on later stages of compromise. Adversaries may prioritize acquiring access to systems that have been determined to lack security monitoring or that have high privileges, or systems that belong to organizations in a particular sector.[1][2]

In some cases, purchasing access to an organization in sectors such as IT contracting, software development, or telecommunications may allow an adversary to compromise additional victims via a Trusted Relationship, Multi-Factor Authentication Interception, or even Supply Chain Compromise.

**Note:** while this technique is distinct from other behaviors such as Purchase Technical Data and Credentials, they may often be used in conjunction (especially where the acquired foothold requires Valid Accounts).

An adversary may add additional local or domain groups to an adversary-controlled account to maintain persistent access to a system or domain.

On Windows, accounts may use the `net localgroup` and `net group` commands to add existing users to local and domain groups.[1][2] On Linux, adversaries may use the `usermod` command for the same purpose.[3]

For example, accounts may be added to the local administrators group on Windows devices to maintain elevated privileges. They may also be added to the Remote Desktop Users group, which allows them to leverage Remote Desktop Protocol to log into the endpoints in the future.[4] Adversaries may also add accounts to VPN user groups to gain future persistence on the network.[5] On Linux, accounts may be added to the sudoers group, allowing them to persistently leverage Sudo and Sudo Caching for elevated privileges.

In Windows environments, machine accounts may also be added to domain groups. This allows the local SYSTEM account to gain privileges on the domain.[6]

Adversaries may abuse the at utility to perform task scheduling for initial or recurring execution of malicious code. The at utility exists as an executable within Windows, Linux, and macOS for scheduling tasks at a specified time and date. Although deprecated in favor of Scheduled Task's schtasks in Windows environments, using at requires that the Task Scheduler service be running, and the user to be logged on as a member of the local Administrators group. In addition to explicitly running the `at` command, adversaries may also schedule a task with at by directly leveraging the Windows Management Instrumentation `Win32_ScheduledJob` WMI class.[1]

On Linux and macOS, at may be invoked by the superuser as well as any users added to the at.allow file. If the at.allow file does not exist, the at.deny file is checked. Every username not listed in at.deny is allowed to invoke at. If the at.deny exists and is empty, global use of at is permitted. If neither file exists (which is often the baseline) only the superuser is allowed to use at.[2]

Adversaries may use at to execute programs at system startup or on a scheduled basis for Persistence. at can also be abused to conduct remote Execution as part of Lateral Movement and/or to run a process under the context of a specified account (such as SYSTEM).

In Linux environments, adversaries may also abuse at to break out of restricted environments by using a task to spawn an interactive system shell or to run system commands. Similarly, at may also be used for Privilege Escalation if the binary is allowed to run as superuser via sudo.[3]

Adversaries may bypass UAC mechanisms to elevate process privileges on system. Windows User Account Control (UAC) allows a program to elevate its privileges (tracked as integrity levels ranging from low to high) to perform a task under administrator-level permissions, possibly by prompting the user for confirmation. The impact to the user ranges from denying the operation under high enforcement to allowing the user to perform the action if they are in the local administrators group and click through the prompt or allowing them to enter an administrator password to complete the action.[1]

If the UAC protection level of a computer is set to anything but the highest level, certain Windows programs can elevate privileges or execute some elevated Component Object Model objects without prompting the user through the UAC notification box.[2][3] An example of this is use of Rundll32 to load a specifically crafted DLL which loads an auto-elevated Component Object Model object and performs a file operation in a protected directory which would typically require elevated access. Malicious software may also be injected into a trusted process to gain elevated privileges without prompting a user.[4]

Many methods have been discovered to bypass UAC. The Github readme page for UACME contains an extensive list of methods[5] that have been discovered and implemented, but may not be a comprehensive list of bypasses. Additional bypass methods are regularly discovered and some used in the wild, such as:

* eventvwr.exe can auto-elevate and execute a specified binary or script.[6][7]

Another bypass is possible through some lateral movement techniques if credentials for an account with administrator privileges are known, since UAC is a single system security mechanism, and the privilege or integrity of a process running on one system will be unknown on remote systems and default to high integrity.[8]

Windows User Account Control (UAC) allows a program to elevate its privileges to perform a task under administrator-level permissions by prompting the user for confirmation. The impact to the user ranges from denying the operation under high enforcement to allowing the user to perform the action if they are in the local administrators group and click through the prompt or allowing them to enter an administrator password to complete the action. [1]

If the UAC protection level of a computer is set to anything but the highest level, certain Windows programs are allowed to elevate privileges or execute some elevated COM objects without prompting the user through the UAC notification box. [2] [3] An example of this is use of rundll32.exe to load a specifically crafted DLL which loads an auto-elevated COM object and performs a file operation in a protected directory which would typically require elevated access. Malicious software may also be injected into a trusted process to gain elevated privileges without prompting a user. [4] Adversaries can use these techniques to elevate privileges to administrator if the target process is unprotected.

Many methods have been discovered to bypass UAC. The Github readme page for UACMe contains an extensive list of methods [5] that have been discovered and implemented within UACMe, but may not be a comprehensive list of bypasses. Additional bypass methods are regularly discovered and some used in the wild, such as:

* eventvwr.exe can auto-elevate and execute a specified binary or script. [6] [7]

Another bypass is possible through some Lateral Movement techniques if credentials for an account with administrator privileges are known, since UAC is a single system security mechanism, and the privilege or integrity of a process running on one system will be unknown on lateral systems and default to high integrity. [8]

Adversaries may clear artifacts associated with previously established persistence on a host system to remove evidence of their activity. This may involve various actions, such as removing services, deleting executables, Modify Registry, Plist File Modification, or other methods of cleanup to prevent defenders from collecting evidence of their persistent presence.[1] Adversaries may also delete accounts previously created to maintain persistence (i.e. Create Account).[2]

In some instances, artifacts of persistence may also be removed once an adversary’s persistence is executed in order to prevent errors with the new instance of the malware.[3]

Adversaries may attempt to get a listing of cloud accounts. Cloud accounts are those created and configured by an organization for use by users, remote support, services, or for administration of resources within a cloud service provider or SaaS application.

With authenticated access there are several tools that can be used to find accounts. The Get-MsolRoleMember PowerShell cmdlet can be used to obtain account names given a role or permissions group in Office 365.[1][2] The Azure CLI (AZ CLI) also provides an interface to obtain user accounts with authenticated access to a domain. The command az ad user list will list all users within a domain.[3][4]

The AWS command aws iam list-users may be used to obtain a list of users in the current account while aws iam list-roles can obtain IAM roles that have a specified path prefix.[5][6] In GCP, gcloud iam service-accounts list and gcloud projects get-iam-policy may be used to obtain a listing of service accounts and users in a project.[7]

Adversaries may disable or modify a firewall within a cloud environment to bypass controls that limit access to cloud resources.

Cloud environments typically utilize restrictive security groups and firewall rules that only allow network activity from trusted IP addresses via expected ports and protocols. An adversary with appropriate permissions may introduce new firewall rules or policies to allow access into a victim cloud environment and/or move laterally from the cloud control plane to the data plane.

For example, an adversary may use a script or utility that creates new ingress rules in existing security groups (or creates new security groups entirely) to allow any TCP/IP connectivity to a cloud-hosted instance. They may also remove networking limitations to support traffic associated with malicious activity (such as cryptomining).[1][2]

Adversaries may attempt to find cloud groups and permission settings. The knowledge of cloud permission groups can help adversaries determine the particular roles of users and groups within an environment, as well as which users are associated with a particular group.

With authenticated access there are several tools that can be used to find permissions groups. The Get-MsolRole PowerShell cmdlet can be used to obtain roles and permissions groups for Exchange and Office 365 accounts [1][2].

Azure CLI (AZ CLI) and the Google Cloud Identity Provider API also provide interfaces to obtain permissions groups. The command az ad user get-member-groups will list groups associated to a user account for Azure while the API endpoint GET https://cloudidentity.googleapis.com/v1/groups lists group resources available to a user for Google.[3][4][5] In AWS, the commands `ListRolePolicies` and `ListAttachedRolePolicies` allow users to enumerate the policies attached to a role.[6]

Adversaries may attempt to list ACLs for objects to determine the owner and other accounts with access to the object, for example, via the AWS GetBucketAcl API [7]. Using this information an adversary can target accounts with permissions to a given object or leverage accounts they have already compromised to access the object.

Adversaries may attempt to access the Cloud Instance Metadata API to collect credentials and other sensitive data.

Most cloud service providers support a Cloud Instance Metadata API which is a service provided to running virtual instances that allows applications to access information about the running virtual instance. Available information generally includes name, security group, and additional metadata including sensitive data such as credentials and UserData scripts that may contain additional secrets. The Instance Metadata API is provided as a convenience to assist in managing applications and is accessible by anyone who can access the instance.[1] A cloud metadata API has been used in at least one high profile compromise.[2]

If adversaries have a presence on the running virtual instance, they may query the Instance Metadata API directly to identify credentials that grant access to additional resources. Additionally, adversaries may exploit a Server-Side Request Forgery (SSRF) vulnerability in a public facing web proxy that allows them to gain access to the sensitive information via a request to the Instance Metadata API.[3]

The de facto standard across cloud service providers is to host the Instance Metadata API at http[:]//169.254.169.254.

Adversaries may attempt to access the Cloud Instance Metadata API to collect credentials and other sensitive data.

Most cloud service providers support a Cloud Instance Metadata API which is a service provided to running virtual instances that allows applications to access information about the running virtual instance. Available information generally includes name, security group, and additional metadata including sensitive data such as credentials and UserData scripts that may contain additional secrets. The Instance Metadata API is provided as a convenience to assist in managing applications and is accessible by anyone who can access the instance.[1]

If adversaries have a presence on the running virtual instance, they may query the Instance Metadata API directly to identify credentials that grant access to additional resources. Additionally, attackers may exploit a Server-Side Request Forgery (SSRF) vulnerability in a public facing web proxy that allows the attacker to gain access to the sensitive information via a request to the Instance Metadata API.[2]

The de facto standard across cloud service providers is to host the Instance Metadata API at http[:]//169.254.169.254.

An adversary may attempt to enumerate the cloud services running on a system after gaining access. These methods can differ from platform-as-a-service (PaaS), to infrastructure-as-a-service (IaaS), or software-as-a-service (SaaS). Many services exist throughout the various cloud providers and can include Continuous Integration and Continuous Delivery (CI/CD), Lambda Functions, Entra ID, etc. They may also include security services, such as AWS GuardDuty and Microsoft Defender for Cloud, and logging services, such as AWS CloudTrail and Google Cloud Audit Logs.

Adversaries may attempt to discover information about the services enabled throughout the environment. Azure tools and APIs, such as the Microsoft Graph API and Azure Resource Manager API, can enumerate resources and services, including applications, management groups, resources and policy definitions, and their relationships that are accessible by an identity.[1][2]

For example, Stormspotter is an open source tool for enumerating and constructing a graph for Azure resources and services, and Pacu is an open source AWS exploitation framework that supports several methods for discovering cloud services.[3][4]

Adversaries may use the information gained to shape follow-on behaviors, such as targeting data or credentials from enumerated services or evading identified defenses through Disable or Modify Tools or Disable or Modify Cloud Log.

Adversaries may abuse built-in CLI tools or API calls to execute malicious commands in containerized environments.

The Docker CLI is used for managing containers via an exposed API point from the `dockerd` daemon. Some common examples of Docker CLI include Docker Desktop CLI and Docker Compose, but users are also able to use SDKs to interact with the API. For example, Docker SDK for Python can be used to run commands within a Python application.[1]

Adversaries may leverage the Docker CLI, API, or SDK to pull or build Docker images (i.e., Ingress Tool Transfer, Build Image on Host), run containers (i.e., Deploy Container), or execute commands inside running containers (i.e., Container Administration Command). In some cases, threat actors may pull legitimate images that include scripts or tools that they can leverage - for example, using an image that includes the `curl` command to download payloads.[2] Adversaries may also utilize `docker inspect` and `docker ps` to scan for cloud environment variables and other running containers (i.e., Container and Resource Discovery).[3][4]

Kubernetes is responsible for the management and orchestration of containers across clusters. The Kubernetes control plane, which manages the state of the cluster and is responsible for scheduling, communication, and resource monitoring, can be invoked directly via the API or indirectly via CLI tools such as `kubectl`. It may also be accessed within client libraries such as Go or Python. By utilizing the API, administrators can interact with resources within the cluster such as listing or creating pods, which is a group of one or more containers. Adversaries call the API server via `curl` or other tools, allowing them to obtain further information about the environment such as pods, deployments, daemonsets, namespaces, or sysvars.[4] They may also run various commands regarding resource management.

Adversaries may search local file systems and remote file shares for files containing insecurely stored credentials. These can be files created by users to store their own credentials, shared credential stores for a group of individuals, configuration files containing passwords for a system or service, or source code/binary files containing embedded passwords.

It is possible to extract passwords from backups or saved virtual machines through OS Credential Dumping.[1] Passwords may also be obtained from Group Policy Preferences stored on the Windows Domain Controller.[2]

In cloud and/or containerized environments, authenticated user and service account credentials are often stored in local configuration and credential files.[3] They may also be found as parameters to deployment commands in container logs.[4] In some cases, these files can be copied and reused on another machine or the contents can be read and then used to authenticate without needing to copy any files.[5]

Adversaries may search local file systems and remote file shares for files containing passwords. These can be files created by users to store their own credentials, shared credential stores for a group of individuals, configuration files containing passwords for a system or service, or source code/binary files containing embedded passwords.

It is possible to extract passwords from backups or saved virtual machines through OS Credential Dumping. [1] Passwords may also be obtained from Group Policy Preferences stored on the Windows Domain Controller. [2]

In cloud environments, authenticated user credentials are often stored in local configuration and credential files. In some cases, these files can be copied and reused on another machine or the contents can be read and then used to authenticate without needing to copy any files. [3]

Adversaries may attempt to access credentials and other sensitive information by abusing a Windows Domain Controller's application programming interface (API)[1] [2] [3] [4] to simulate the replication process from a remote domain controller using a technique called DCSync.

Members of the Administrators, Domain Admins, and Enterprise Admin groups or computer accounts on the domain controller are able to run DCSync to pull password data[5] from Active Directory, which may include current and historical hashes of potentially useful accounts such as KRBTGT and Administrators. The hashes can then in turn be used to create a Golden Ticket for use in Pass the Ticket[6] or change an account's password as noted in Account Manipulation.[7]

DCSync functionality has been included in the "lsadump" module in Mimikatz.[8] Lsadump also includes NetSync, which performs DCSync over a legacy replication protocol.[9]

Adversaries may disable or modify a firewall within a cloud environment to bypass controls that limit access to cloud resources. Cloud firewalls are separate from system firewalls that are described in Disable or Modify System Firewall.

Cloud environments typically utilize restrictive security groups and firewall rules that only allow network activity from trusted IP addresses via expected ports and protocols. An adversary with appropriate permissions may introduce new firewall rules or policies to allow access into a victim cloud environment and/or move laterally from the cloud control plane to the data plane. For example, an adversary may use a script or utility that creates new ingress rules in existing security groups (or creates new security groups entirely) to allow any TCP/IP connectivity to a cloud-hosted instance.[1] They may also remove networking limitations to support traffic associated with malicious activity (such as cryptomining).[2][1]

Modifying or disabling a cloud firewall may enable adversary C2 communications, lateral movement, and/or data exfiltration that would otherwise not be allowed. It may also be used to open up resources for Brute Force or Endpoint Denial of Service.

Adversaries may attempt to get a listing of domain accounts. This information can help adversaries determine which domain accounts exist to aid in follow-on behavior such as targeting specific accounts which possess particular privileges.

Commands such as net user /domain and net group /domain of the Net utility, dscacheutil -q group on macOS, and ldapsearch on Linux can list domain users and groups. PowerShell cmdlets including Get-ADUser and Get-ADGroupMember may enumerate members of Active Directory groups.[1]

Adversaries may attempt to find domain-level groups and permission settings. The knowledge of domain-level permission groups can help adversaries determine which groups exist and which users belong to a particular group. Adversaries may use this information to determine which users have elevated permissions, such as domain administrators.

Commands such as net group /domain of the Net utility, dscacheutil -q group on macOS, and ldapsearch on Linux can list domain-level groups.

Adversaries may modify the configuration settings of a domain or identity tenant to evade defenses and/or escalate privileges in centrally managed environments. Such services provide a centralized means of managing identity resources such as devices and accounts, and often include configuration settings that may apply between domains or tenants such as trust relationships, identity syncing, or identity federation.

Modifications to domain or tenant settings may include altering domain Group Policy Objects (GPOs) in Microsoft Active Directory (AD) or changing trust settings for domains, including federation trusts relationships between domains or tenants.

With sufficient permissions, adversaries can modify domain or tenant policy settings. Since configuration settings for these services apply to a large number of identity resources, there are a great number of potential attacks malicious outcomes that can stem from this abuse. Examples of such abuse include:

* modifying GPOs to push a malicious Scheduled Task to computers throughout the domain environment[1][2][3] * modifying domain trusts to include an adversary-controlled domain, allowing adversaries to forge access tokens that will subsequently be accepted by victim domain resources[4] * changing configuration settings within the AD environment to implement a Rogue Domain Controller. * adding new, adversary-controlled federated identity providers to identity tenants, allowing adversaries to authenticate as any user managed by the victim tenant [5]

Adversaries may temporarily modify domain or tenant policy, carry out a malicious action(s), and then revert the change to remove suspicious indicators.

Adversaries may acquire domains that can be used during targeting. Domain names are the human readable names used to represent one or more IP addresses. They can be purchased or, in some cases, acquired for free.

Adversaries may use acquired domains for a variety of purposes, including for Phishing, Drive-by Compromise, and Command and Control.[1] Adversaries may choose domains that are similar to legitimate domains, including through use of homoglyphs or use of a different top-level domain (TLD).[2][3] Typosquatting may be used to aid in delivery of payloads via Drive-by Compromise. Adversaries may also use internationalized domain names (IDNs) and different character sets (e.g. Cyrillic, Greek, etc.) to execute "IDN homograph attacks," creating visually similar lookalike domains used to deliver malware to victim machines.[4][5][6][7][8]

Different URIs/URLs may also be dynamically generated to uniquely serve malicious content to victims (including one-time, single use domain names).[9][10][11][12]

Adversaries may also acquire and repurpose expired domains, which may be potentially already allowlisted/trusted by defenders based on an existing reputation/history.[13][14][15][16]

Domain registrars each maintain a publicly viewable database that displays contact information for every registered domain. Private WHOIS services display alternative information, such as their own company data, rather than the owner of the domain. Adversaries may use such private WHOIS services to obscure information about who owns a purchased domain. Adversaries may further interrupt efforts to track their infrastructure by using varied registration information and purchasing domains with different domain registrars.[17]

In addition to legitimately purchasing a domain, an adversary may register a new domain in a compromised environment. For example, in AWS environments, adversaries may leverage the Route53 domain service to register a domain and create hosted zones pointing to resources of the threat actor’s choosing.[18]

Adversaries may gain access to a system during a drive-by compromise, when a user visits a website as part of a regular browsing session. With this technique, the user's web browser is targeted and exploited simply by visiting the compromised website.

The adversary may target a specific community, such as trusted third party suppliers or other industry specific groups, which often visit the target website. This kind of targeted attack relies on a common interest, and is known as a strategic web compromise or watering hole attack.

The National Cyber Awareness System (NCAS) has issued a Technical Alert (TA) regarding Russian government cyber activity targeting critical infrastructure sectors. [1] Analysis by DHS and FBI has noted two distinct categories of victims in the Dragonfly campaign on the Western energy sector: staging and intended targets. The adversary targeted the less secure networks of staging targets, including trusted third-party suppliers and related peripheral organizations. Initial access to the intended targets used watering hole attacks to target process control, ICS, and critical infrastructure related trade publications and informational websites.