System Network Connections Discovery
Adversaries may attempt to get a listing of network connections to or from the compromised system they are currently accessing or from remote systems by querying for information over the network.
Mac and Linux
In Mac and Linux,
lsof can be used to list current connections.
who -a and
w can be used to show which users are currently logged in, similar to "net session".
nbtstat can be used to discover current NetBIOS sessions.
Identify unnecessary system utilities or potentially malicious software that may be used to acquire information about network connections, and audit and/or block them by using whitelisting  tools, like AppLocker,   or Software Restriction Policies  where appropriate. 
System and network discovery techniques normally occur throughout an operation as an adversary learns the environment. Data and events should not be viewed in isolation, but as part of a chain of behavior that could lead to other activities, such as Lateral Movement, based on the information obtained.
Monitor processes and command-line arguments for actions that could be taken to gather system and network information. Remote access tools with built-in features may interact directly with the Windows API to gather information. Information may also be acquired through Windows system management tools such as Windows Management Instrumentation and PowerShell.
- FireEye Threat Intelligence. (2015, December 1). China-based Cyber Threat Group Uses Dropbox for Malware Communications and Targets Hong Kong Media Outlets. Retrieved December 4, 2015.
- Symantec Security Response. (2016, September 6). Buckeye cyberespionage group shifts gaze from US to Hong Kong. Retrieved September 26, 2016.
- Chen, X., Scott, M., Caselden, D.. (2014, April 26). New Zero-Day Exploit targeting Internet Explorer Versions 9 through 11 Identified in Targeted Attacks. Retrieved January 14, 2016.
- Yates, M. (2017, June 18). APT3 Uncovered: The code evolution of Pirpi. Retrieved September 28, 2017.
- F-Secure Labs. (2014). BlackEnergy & Quedagh: The convergence of crimeware and APT attacks. Retrieved March 24, 2016.
- Baumgartner, K. and Garnaeva, M.. (2014, November 3). BE2 custom plugins, router abuse, and target profiles. Retrieved March 24, 2016.
- Grunzweig, J. (2018, January 31). Comnie Continues to Target Organizations in East Asia. Retrieved June 7, 2018.
- Symantec Security Response. (2011, November). W32.Duqu: The precursor to the next Stuxnet. Retrieved September 17, 2015.
- Mercer, W., Rascagneres, P. (2018, April 26). GravityRAT - The Two-Year Evolution Of An APT Targeting India. Retrieved May 16, 2018.
- Villeneuve, N., Bennett, J. T., Moran, N., Haq, T., Scott, M., & Geers, K. (2014). OPERATION “KE3CHANG”: Targeted Attacks Against Ministries of Foreign Affairs. Retrieved November 12, 2014.
- Smallridge, R. (2018, March 10). APT15 is alive and strong: An analysis of RoyalCli and RoyalDNS. Retrieved April 4, 2018.
- Symantec Security Response Attack Investigation Team. (2018, April 23). New Orangeworm attack group targets the healthcare sector in the U.S., Europe, and Asia. Retrieved May 8, 2018.
- PwC and BAE Systems. (2017, April). Operation Cloud Hopper. Retrieved April 5, 2017.
- Savill, J. (1999, March 4). Net.exe reference. Retrieved September 22, 2015.
- Microsoft. (n.d.). Netstat. Retrieved April 17, 2016.
- Falcone, R. and Lee, B.. (2016, May 26). The OilRig Campaign: Attacks on Saudi Arabian Organizations Deliver Helminth Backdoor. Retrieved May 3, 2017.
- 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.
- 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.
- Nicolas Verdier. (n.d.). Retrieved January 29, 2018.
- Trend Micro. (2017, February 27). RATANKBA: Delving into Large-scale Watering Holes against Enterprises. Retrieved May 22, 2018.
- PwC and BAE Systems. (2017, April). Operation Cloud Hopper: Technical Annex. Retrieved April 13, 2017.
- Kaspersky Lab's Global Research & Analysis Team. (2016, August 9). The ProjectSauron APT. Technical Analysis. Retrieved August 17, 2016.
- Falcone, R. and Wartell, R.. (2015, July 27). Observations on CVE-2015-3113, Prior Zero-Days and the Pirpi Payload. Retrieved January 22, 2016.
- Blasco, J. (2011, December 12). Another Sykipot sample likely targeting US federal agencies. Retrieved March 28, 2016.
- Counter Threat Unit Research Team. (2017, June 27). BRONZE UNION Cyberespionage Persists Despite Disclosures. Retrieved July 13, 2017.
- Kaspersky Lab's Global Research and Analysis Team. (2014, August 7). The Epic Turla Operation: Solving some of the mysteries of Snake/Uroburos. Retrieved December 11, 2014.
- Yagi, J. (2014, August 24). Trojan.Volgmer. Retrieved July 16, 2018.
- Beechey, J. (2010, December). Application Whitelisting: Panacea or Propaganda?. Retrieved November 18, 2014.
- Tomonaga, S. (2016, January 26). Windows Commands Abused by Attackers. Retrieved February 2, 2016.
- NSA Information Assurance Directorate. (2014, August). Application Whitelisting Using Microsoft AppLocker. Retrieved March 31, 2016.
- Corio, C., & Sayana, D. P. (2008, June). Application Lockdown with Software Restriction Policies. Retrieved November 18, 2014.
- Microsoft. (2012, June 27). Using Software Restriction Policies and AppLocker Policies. Retrieved April 7, 2016.