Adversaries may obtain and abuse credentials of existing accounts as a means of gaining Initial Access, Persistence, Privilege Escalation, or Defense Evasion. Compromised credentials may be used to bypass access controls placed on various resources on systems within the network and may even be used for persistent access to remote systems and externally available services, such as VPNs, Outlook Web Access and remote desktop. Compromised credentials may also grant an adversary increased privilege to specific systems or access to restricted areas of the network. Adversaries may choose not to use malware or tools in conjunction with the legitimate access those credentials provide to make it harder to detect their presence.
The overlap of permissions for local, domain, and cloud accounts across a network of systems is of concern because the adversary may be able to pivot across accounts and systems to reach a high level of access (i.e., domain or enterprise administrator) to bypass access controls set within the enterprise. 
APT28 has used legitimate credentials to gain initial access, maintain access, and exfiltrate data from a victim network. The group has specifically used credentials stolen through a spearphishing email to login to the DCCC network. The group has also leveraged default manufacturer's passwords to gain initial access to corporate networks via IoT devices such as a VOIP phone, printer, and video decoder.
Adversaries can instruct Duqu to spread laterally by copying itself to shares it has enumerated and for which it has obtained legitimate credentials (via keylogging or other means). The remote host is then infected by using the compromised credentials to schedule a task on remote machines that executes the malware.
|Application Developer Guidance||
Ensure that applications do not store sensitive data or credentials insecurely. (e.g. plaintext credentials in code, published credentials in repositories, or credentials in public cloud storage).
Applications and appliances that utilize default username and password should be changed immediately after the installation, and before deployment to a production environment.  When possible, applications that use SSH keys should be updated periodically and properly secured.
|Privileged Account Management||
Audit domain and local accounts as well as their permission levels routinely to look for situations that could allow an adversary to gain wide access by obtaining credentials of a privileged account.   These audits should also include if default accounts have been enabled, or if new local accounts are created that have not be authorized. Follow best practices for design and administration of an enterprise network to limit privileged account use across administrative tiers. 
Configure robust, consistent account activity audit policies across the enterprise and with externally accessible services.  Look for suspicious account behavior across systems that share accounts, either user, admin, or service accounts. Examples: one account logged into multiple systems simultaneously; multiple accounts logged into the same machine simultaneously; accounts logged in at odd times or outside of business hours. Activity may be from interactive login sessions or process ownership from accounts being used to execute binaries on a remote system as a particular account. Correlate other security systems with login information (e.g., a user has an active login session but has not entered the building or does not have VPN access).
Perform regular audits of domain and local system accounts to detect accounts that may have been created by an adversary for persistence. Checks on these accounts could also include whether default accounts such as Guest have been activated. These audits should also include checks on any appliances and applications for default credentials or SSH keys, and if any are discovered, they should be updated immediately.
- Microsoft. (2016, April 15). Attractive Accounts for Credential Theft. Retrieved June 3, 2016.
- Adair, S. (2017, February 17). Detecting and Responding to Advanced Threats within Exchange Environments. Retrieved March 20, 2017.
- Hacquebord, F.. (2017, April 25). Two Years of Pawn Storm: Examining an Increasingly Relevant Threat. Retrieved May 3, 2017.
- Mueller, R. (2018, July 13). Indictment - United States of America vs. VIKTOR BORISOVICH NETYKSHO, et al. Retrieved September 13, 2018.
- MSRC Team. (2019, August 5). Corporate IoT – a path to intrusion. Retrieved August 16, 2019.
- Davis, S. and Carr, N. (2017, September 21). APT33: New Insights into Iranian Cyber Espionage Group. Retrieved February 15, 2018.
- Ackerman, G., et al. (2018, December 21). OVERRULED: Containing a Potentially Destructive Adversary. Retrieved January 17, 2019.
- Hawley et al. (2019, January 29). APT39: An Iranian Cyber Espionage Group Focused on Personal Information. Retrieved February 19, 2019.
- Fraser, N., et al. (2019, August 7). Double DragonAPT41, a dual espionage and cyber crime operation APT41. Retrieved September 23, 2019.
- Kaspersky Lab's Global Research and Analysis Team. (2015, February). CARBANAK APT THE GREAT BANK ROBBERY. Retrieved August 23, 2018.
- Cycraft. (2020, April 15). APT Group Chimera - APT Operation Skeleton key Targets Taiwan Semiconductor Vendors. Retrieved August 24, 2020.
- US-CERT. (2018, March 16). Alert (TA18-074A): Russian Government Cyber Activity Targeting Energy and Other Critical Infrastructure Sectors. Retrieved June 6, 2018.
- Symantec Security Response. (2011, November). W32.Duqu: The precursor to the next Stuxnet. Retrieved September 17, 2015.
- FireEye iSIGHT Intelligence. (2017, June 16). FIN10: Anatomy of a Cyber Extortion Operation. Retrieved June 25, 2017.
- Vengerik, B. et al.. (2014, December 5). Hacking the Street? FIN4 Likely Playing the Market. Retrieved December 17, 2018.
- Vengerik, B. & Dennesen, K.. (2014, December 5). Hacking the Street? FIN4 Likely Playing the Market. Retrieved January 15, 2019.
- Scavella, T. and Rifki, A. (2017, July 20). Are you Ready to Respond? (Webinar). Retrieved October 4, 2017.
- Higgins, K. (2015, October 13). Prolific Cybercrime Gang Favors Legit Login Credentials. Retrieved October 4, 2017.
- Bromiley, M. and Lewis, P. (2016, October 7). Attacking the Hospitality and Gaming Industries: Tracking an Attacker Around the World in 7 Years. Retrieved October 6, 2017.
- FireEye Threat Intelligence. (2016, April). Follow the Money: Dissecting the Operations of the Cyber Crime Group FIN6. Retrieved June 1, 2016.
- McKeague, B. et al. (2019, April 5). Pick-Six: Intercepting a FIN6 Intrusion, an Actor Recently Tied to Ryuk and LockerGoga Ransomware. Retrieved April 17, 2019.
- Visa Public. (2019, February). FIN6 Cybercrime Group Expands Threat to eCommerce Merchants. Retrieved September 16, 2019.
- Elovitz, S. & Ahl, I. (2016, August 18). Know Your Enemy: New Financially-Motivated & Spear-Phishing Group. Retrieved February 26, 2018.
- Axel F, Pierre T. (2017, October 16). Leviathan: Espionage actor spearphishes maritime and defense targets. Retrieved February 15, 2018.
- Anomali Labs. (2018, December 6). Pulling Linux Rabbit/Rabbot Malware Out of a Hat. Retrieved March 4, 2019.
- PwC and BAE Systems. (2017, April). Operation Cloud Hopper. Retrieved April 5, 2017.
- McAfee® Foundstone® Professional Services and McAfee Labs™. (2011, February 10). Global Energy Cyberattacks: “Night Dragon”. Retrieved February 19, 2018.
- Unit 42. (2017, December 15). Unit 42 Playbook Viewer. Retrieved December 20, 2017.
- Davis, S. and Caban, D. (2017, December 19). APT34 - New Targeted Attack in the Middle East. Retrieved December 20, 2017.
- Bizeul, D., Fontarensky, I., Mouchoux, R., Perigaud, F., Pernet, C. (2014, July 11). Eye of the Tiger. Retrieved September 29, 2015.
- US-CERT. (2016, February 25). ICS Alert (IR-ALERT-H-16-056-01) Cyber-Attack Against Ukrainian Critical Infrastructure. Retrieved June 10, 2020.
- Symantec Security Response. (2015, July 13). “Forkmeiamfamous”: Seaduke, latest weapon in the Duke armory. Retrieved July 22, 2015.
- Group-IB. (2018, September). Silence: Moving Into the Darkside. Retrieved May 5, 2020.
- Cybereason Nocturnus. (2019, June 25). Operation Soft Cell: A Worldwide Campaign Against Telecommunications Providers. Retrieved July 18, 2019.
- DiMaggio, J.. (2016, May 17). Indian organizations targeted in Suckfly attacks. Retrieved August 3, 2016.
- Miller, S, et al. (2019, April 10). TRITON Actor TTP Profile, Custom Attack Tools, Detections, and ATT&CK Mapping. Retrieved April 16, 2019.
- Dell SecureWorks Counter Threat Unit Threat Intelligence. (2015, August 5). Threat Group-3390 Targets Organizations for Cyberespionage. Retrieved August 18, 2018.
- John, E. and Carvey, H. (2019, May 30). Unraveling the Spiderweb: Timelining ATT&CK Artifacts Used by GRIM SPIDER. Retrieved May 12, 2020.
- undefined. (n.d.). Risks of Default Passwords on the Internet. Retrieved April 12, 2019.
- Microsoft. (2016, April 16). Implementing Least-Privilege Administrative Models. Retrieved June 3, 2016.
- Plett, C., Poggemeyer, L. (12, October 26). Securing Privileged Access Reference Material. Retrieved April 25, 2017.
- Microsoft. (2016, April 15). Audit Policy Recommendations. Retrieved June 3, 2016.