PowerShell is a powerful interactive command-line interface and scripting environment included in the Windows operating system.  Adversaries can use PowerShell to perform a number of actions, including discovery of information and execution of code. Examples include the Start-Process cmdlet which can be used to run an executable and the Invoke-Command cmdlet which runs a command locally or on a remote computer.
PowerShell may also be used to download and run executables from the Internet, which can be executed from disk or in memory without touching disk.
Administrator permissions are required to use PowerShell to connect to remote systems.
PowerShell commands/scripts can also be executed without directly invoking the powershell.exe binary through interfaces to PowerShell's underlying System.Management.Automation assembly exposed through the .NET framework and Windows Common Language Interface (CLI).  
It may be possible to remove PowerShell from systems when not needed, but a review should be performed to assess the impact to an environment, since it could be in use for many legitimate purposes and administrative functions. When PowerShell is necessary, restrict PowerShell execution policy to administrators and to only execute signed scripts. Be aware that there are methods of bypassing the PowerShell execution policy, depending on environment configuration.  Disable/restrict the WinRM Service to help prevent uses of PowerShell for remote execution.
If proper execution policy is set, adversaries will likely be able to define their own execution policy if they obtain administrator or system access, either through the Registry or at the command line. This change in policy on a system may be a way to detect malicious use of PowerShell. If PowerShell is not used in an environment, then simply looking for PowerShell execution may detect malicious activity.
It is also beneficial to turn on PowerShell logging to gain increased fidelity in what occurs during execution (which is applied to .NET invocations).  PowerShell 5.0 introduced enhanced logging capabilities, and some of those features have since been added to PowerShell 4.0. Earlier versions of PowerShell do not have many logging features.  An organization can gather PowerShell execution details in a data analytic platform to supplement it with other data.
- Microsoft. (n.d.). Windows PowerShell Scripting. Retrieved April 28, 2016.
- PowerSploit. (n.d.). Retrieved December 4, 2014.
- Haight, J. (2016, April 21). PS>Attack. Retrieved June 1, 2016.
- Warner, J.. (2015, January 6). Inexorable PowerShell – A Red Teamer’s Tale of Overcoming Simple AppLocker Policies. Retrieved December 8, 2018.
- Christensen, L.. (2015, December 28). The Evolution of Offensive PowerShell Invocation. Retrieved December 8, 2018.
- Babinec, K. (2014, April 28). Executing PowerShell scripts from C#. Retrieved April 22, 2019.
- Ahl, I. (2017, June 06). Privileges and Credentials: Phished at the Request of Counsel. Retrieved May 17, 2018.
- Lee, B., Falcone, R. (2018, June 06). Sofacy Group’s Parallel Attacks. Retrieved June 18, 2018.
- Symantec Security Response. (2015, July 13). “Forkmeiamfamous”: Seaduke, latest weapon in the Duke armory. Retrieved July 22, 2015.
- Dunwoody, M. and Carr, N.. (2016, September 27). No Easy Breach DerbyCon 2016. Retrieved October 4, 2016.
- Dunwoody, M., et al. (2018, November 19). Not So Cozy: An Uncomfortable Examination of a Suspected APT29 Phishing Campaign. Retrieved November 27, 2018.
- Moran, N., et al. (2014, November 21). Operation Double Tap. Retrieved January 14, 2016.
- Carr, N.. (2017, May 14). Cyber Espionage is Alive and Well: APT32 and the Threat to Global Corporations. Retrieved June 18, 2017.
- Dahan, A. (2017, May 24). OPERATION COBALT KITTY: A LARGE-SCALE APT IN ASIA CARRIED OUT BY THE OCEANLOTUS GROUP. Retrieved November 5, 2018.
- Dahan, A. (2017). Operation Cobalt Kitty. Retrieved December 27, 2018.
- Security Response attack Investigation Team. (2019, March 27). Elfin: Relentless Espionage Group Targets Multiple Organizations in Saudi Arabia and U.S.. Retrieved April 10, 2019.
- Settle, A., et al. (2016, August 8). MONSOON - Analysis Of An APT Campaign. Retrieved September 22, 2016.
- Sardiwal, M, et al. (2017, December 7). New Targeted Attack in the Middle East by APT34, a Suspected Iranian Threat Group, Using CVE-2017-11882 Exploit. Retrieved December 20, 2017.
- Wilhoit, K. and Falcone, R. (2018, September 12). OilRig Uses Updated BONDUPDATER to Target Middle Eastern Government. Retrieved February 18, 2019.
- Counter Threat Unit Research Team. (2017, October 12). BRONZE BUTLER Targets Japanese Enterprises. Retrieved January 4, 2018.
- Svajcer, V. (2018, July 31). Multiple Cobalt Personality Disorder. Retrieved September 5, 2018.
- Positive Technologies. (2017, August 16). Cobalt Strikes Back: An Evolving Multinational Threat to Finance. Retrieved September 5, 2018.
- Positive Technologies. (2016, December 16). Cobalt Snatch. Retrieved October 9, 2018.
- Matveeva, V. (2017, August 15). Secrets of Cobalt. Retrieved October 10, 2018.
- Klijnsma, Y.. (2018, January 16). First Activities of Cobalt Group in 2018: Spear Phishing Russian Banks. Retrieved October 10, 2018.
- Giagone, R., Bermejo, L., and Yarochkin, F. (2017, November 20). Cobalt Strikes Again: Spam Runs Use Macros and CVE-2017-8759 Exploit Against Russian Banks. Retrieved March 7, 2019.
- Strategic Cyber LLC. (2017, March 14). Cobalt Strike Manual. Retrieved May 24, 2017.
- Falcone, R., et al. (2018, July 27). New Threat Actor Group DarkHydrus Targets Middle East Government. Retrieved August 2, 2018.
- Unit 42. (2017, December 15). Unit 42 Playbook Viewer. Retrieved December 20, 2017.
- Alperovitch, D. (2014, July 7). Deep in Thought: Chinese Targeting of National Security Think Tanks. Retrieved November 12, 2014.
- ClearSky Cyber Security. (2017, December). Charming Kitten. Retrieved December 27, 2017.
- 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. (2017, September 6). Dragonfly: Western energy sector targeted by sophisticated attack group. Retrieved September 9, 2017.
- US-CERT. (2017, October 20). Alert (TA17-293A): Advanced Persistent Threat Activity Targeting Energy and Other Critical Infrastructure Sectors. Retrieved November 2, 2017.
- Symantec. (2018, July 18). The Evolution of Emotet: From Banking Trojan to Threat Distributor. Retrieved March 25, 2019.
- Trend Micro. (2019, January 16). Exploring Emotet's Activities . Retrieved March 25, 2019.
- Özarslan, S. (2018, December 21). The Christmas Card you never wanted - A new wave of Emotet is back to wreak havoc. Retrieved March 25, 2019.
- Donohue, B.. (2019, February 13). https://redcanary.com/blog/stopping-emotet-before-it-moves-laterally/. Retrieved March 25, 2019.
- Schroeder, W., Warner, J., Nelson, M. (n.d.). Github PowerShellEmpire. Retrieved April 28, 2016.
- The Australian Cyber Security Centre (ACSC), the Canadian Centre for Cyber Security (CCCS), the New Zealand National Cyber Security Centre (NZ NCSC), CERT New Zealand, the UK National Cyber Security Centre (UK NCSC) and the US National Cybersecurity and Communications Integration Center (NCCIC). (2018, October 11). Joint report on publicly available hacking tools. Retrieved March 11, 2019.
- FireEye iSIGHT Intelligence. (2017, June 16). FIN10: Anatomy of a Cyber Extortion Operation. Retrieved June 25, 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.
- Carr, N., et al. (2017, April 24). FIN7 Evolution and the Phishing LNK. Retrieved April 24, 2017.
- Gorelik, M.. (2017, June 9). FIN7 Takes Another Bite at the Restaurant Industry. Retrieved July 13, 2017.
- Bohannon, D. & Carr N. (2017, June 30). Obfuscation in the Wild: Targeted Attackers Lead the Way in Evasion Techniques. Retrieved February 12, 2018.
- Elovitz, S. & Ahl, I. (2016, August 18). Know Your Enemy: New Financially-Motivated & Spear-Phishing Group. Retrieved February 26, 2018.
- Symantec Security Response. (2018, October 10). Gallmaker: New Attack Group Eschews Malware to Live off the Land. Retrieved November 27, 2018.
- Falcone, R., et al. (2018, August 02). The Gorgon Group: Slithering Between Nation State and Cybercrime. Retrieved August 7, 2018.
- FireEye Labs. (2015, July). HAMMERTOSS: Stealthy Tactics Define a Russian Cyber Threat Group. Retrieved September 17, 2015.
- Falcone, R. and Lee, B.. (2016, May 26). The OilRig Campaign: Attacks on Saudi Arabian Organizations Deliver Helminth Backdoor. Retrieved May 3, 2017.
- Rascagneres, P. (2017, May 03). KONNI: A Malware Under The Radar For Years. Retrieved November 5, 2018.
- Axel F, Pierre T. (2017, October 16). Leviathan: Espionage actor spearphishes maritime and defense targets. Retrieved February 15, 2018.
- FireEye. (2018, March 16). Suspected Chinese Cyber Espionage Group (TEMP.Periscope) Targeting U.S. Engineering and Maritime Industries. Retrieved April 11, 2018.
- Lee, B. and Falcone, R. (2017, February 15). Magic Hound Campaign Attacks Saudi Targets. Retrieved December 27, 2017.
- Mandiant. (2018). Mandiant M-Trends 2018. Retrieved July 9, 2018.
- PwC and BAE Systems. (2017, April). Operation Cloud Hopper: Technical Annex. Retrieved April 13, 2017.
- ESET, et al. (2018, January). Diplomats in Eastern Europe bitten by a Turla mosquito. Retrieved July 3, 2018.
- Singh, S. et al.. (2018, March 13). Iranian Threat Group Updates Tactics, Techniques and Procedures in Spear Phishing Campaign. Retrieved April 11, 2018.
- Villanueva, M., Co, M. (2018, June 14). Another Potential MuddyWater Campaign uses Powershell-based PRB-Backdoor. Retrieved July 3, 2018.
- Kaspersky Lab's Global Research & Analysis Team. (2018, October 10). MuddyWater expands operations. Retrieved November 2, 2018.
- Symantec DeepSight Adversary Intelligence Team. (2018, December 10). Seedworm: Group Compromises Government Agencies, Oil & Gas, NGOs, Telecoms, and IT Firms. Retrieved December 14, 2018.
- ClearSky Cyber Security. (2018, November). MuddyWater Operations in Lebanon and Oman: Using an Israeli compromised domain for a two-stage campaign. Retrieved November 29, 2018.
- Falcone, R. and Lee, B. (2017, October 9). OilRig Group Steps Up Attacks with New Delivery Documents and New Injector Trojan. Retrieved January 8, 2018.
- Meyers, A. (2018, November 27). Meet CrowdStrike’s Adversary of the Month for November: HELIX KITTEN. Retrieved December 18, 2018.
- Cymmetria. (2016). Unveiling Patchwork - The Copy-Paste APT. Retrieved August 3, 2016.
- Lunghi, D., et al. (2017, December). Untangling the Patchwork Cyberespionage Group. Retrieved July 10, 2018.
- Kaspersky Lab's Global Research and Analysis Team. (2016, February 9). Poseidon Group: a Targeted Attack Boutique specializing in global cyber-espionage. Retrieved March 16, 2016.
- Dunwoody, M.. (2017, April 3). Dissecting One of APT29’s Fileless WMI and PowerShell Backdoors (POSHSPY). Retrieved April 5, 2017.
- Miller, S., et al. (2017, March 7). FIN7 Spear Phishing Campaign Targets Personnel Involved in SEC Filings. Retrieved March 8, 2017.
- Brumaghin, E. and Grady, C.. (2017, March 2). Covert Channels and Poor Decisions: The Tale of DNSMessenger. Retrieved March 8, 2017.
- PowerShellMafia. (2012, May 26). PowerSploit - A PowerShell Post-Exploitation Framework. Retrieved February 6, 2018.
- PowerSploit. (n.d.). PowerSploit. Retrieved February 6, 2018.
- Lancaster, T.. (2017, November 14). Muddying the Water: Targeted Attacks in the Middle East. Retrieved March 15, 2018.
- Ackerman, G., et al. (2018, December 21). OVERRULED: Containing a Potentially Destructive Adversary. Retrieved January 17, 2019.
- Nicolas Verdier. (n.d.). Retrieved January 29, 2018.
- Lee, B., Falcone, R. (2018, July 25). OilRig Targets Technology Service Provider and Government Agency with QUADAGENT. Retrieved August 9, 2018.
- Lei, C., et al. (2018, January 24). Lazarus Campaign Targeting Cryptocurrencies Reveals Remote Controller Tool, an Evolved RATANKBA, and More. Retrieved May 22, 2018.
- Trend Micro. (2017, February 27). RATANKBA: Delving into Large-scale Watering Holes against Enterprises. Retrieved May 22, 2018.
- Lee, B., Falcone, R. (2019, January 18). DarkHydrus delivers new Trojan that can use Google Drive for C2 communications. Retrieved April 17, 2019.
- Marczak, B. and Scott-Railton, J.. (2016, May 29). Keep Calm and (Don’t) Enable Macros: A New Threat Actor Targets UAE Dissidents. Retrieved June 8, 2016.
- Axel F. (2017, April 27). APT Targets Financial Analysts with CVE-2017-0199. Retrieved February 15, 2018.
- FireEye Intelligence . (2018, October 23). TRITON Attribution: Russian Government-Owned Lab Most Likely Built Custom Intrusion Tools for TRITON Attackers. Retrieved April 16, 2019.
- Miller, S, et al. (2019, April 10). TRITON Actor TTP Profile, Custom Attack Tools, Detections, and ATT&CK Mapping. Retrieved April 16, 2019.
- Counter Threat Unit Research Team. (2017, June 27). BRONZE UNION Cyberespionage Persists Despite Disclosures. Retrieved July 13, 2017.
- Security Response Attack Investigation Team. (2018, June 19). Thrip: Espionage Group Hits Satellite, Telecoms, and Defense Companies. Retrieved July 10, 2018.
- ESET Research. (2018, May 22). Turla Mosquito: A shift towards more generic tools. Retrieved July 3, 2018.
- Xiao, C. (2018, September 17). Xbash Combines Botnet, Ransomware, Coinmining in Worm that Targets Linux and Windows. Retrieved November 14, 2018.
- Brumaghin, E., et al. (2017, November 02). Poisoning the Well: Banking Trojan Targets Google Search Results. Retrieved November 5, 2018.
- Sutherland, S. (2014, September 9). 15 Ways to Bypass the PowerShell Execution Policy. Retrieved July 23, 2015.
- Malware Archaeology. (2016, June). WINDOWS POWERSHELL LOGGING CHEAT SHEET - Win 7/Win 2008 or later. Retrieved June 24, 2016.
- Dunwoody, M. (2016, February 11). GREATER VISIBILITY THROUGH POWERSHELL LOGGING. Retrieved February 16, 2016.