Guest Article

Detecting Credential Stealing Attacks through Active In-Network Defense

By Chintan Shah, Security Researcher with McAfee Intrusion Prevention System

Today, enterprises tend to use multiple layers of security defenses, ranging from perimeter defense on network entry points to host based security solutions deployed at the end user’s machines to counter the ever-increasing threats. This includes inline traffic filtering and management security solutions deployed at access and distribution layers in the network, as well as out of band solutions like NAC, SIEM or User Behavior Analysis to provide identity-based network access and gain more visibility into the user’s access to critical network resources. However, layered security defenses face the major and recurring challenge of detecting newer exploitation techniques as they heavily rely on known behaviors. Additionally, yet another significant challenge facing the enterprise network is detecting post-exploitation activities, after perimeter security is compromised.

Post initial compromise, to be able to execute meaningful attacks, attackers would need to steal credentials to move laterally inside the network, access critical network assets and eventually exfiltrate data. They will use several sophisticated techniques to perform internal reconnaissance and remote code execution on critical resources, which range from using legitimate operating system tools to discover network assets to using novel code execution techniques on the target. Consequently, differentiating between the legitimate and malicious use of Windows’ internal tools and services becomes a high priority for enterprise networks.

To tackle this long-standing problem of detecting lateral movement, enterprise networks must formulate active in-network defense strategies to effectively prevent attackers from accessing critical network resources. Network Deception is one such defensive approach which could potentially prove to be an effective solution to detect credential theft attacks. Detecting credential stealing attacks with deception essentially requires building the necessary infrastructure by placing the decoy systems within the same network as production assets and configuring them with decoy contents to lure the attackers towards the decoy machines and services. Accurately configuring and tuning the deceptive network can deflect the attacker’s lateral movement path towards the deceptive services, consequently allowing the attackers to engage with the deceptive network, helping enterprises protect production assets. MITRE Shield, a knowledge base maintained by MITRE for active defense techniques highlights many of the methods in adversary engagement. Some of the techniques described by MITRE Shield Matrix with respect to network deception are as below:

MITRE Shield Description ATT&CK Technique

Decoy Account – DTE0010 A decoy account is created for defensive or deceptive purposes. The decoy account can be used to make a system, service, or software look more realistic or to entice an action Account Discovery, Reconnaissance

Decoy Credentials – DTE0012 Seed a target system with credentials (such as Credential Access, Privilege Escalation

username/password, browser tokens, and other forms of authentication data)

Decoy Diversity – DTE0013 deployment of decoy systems with varying Operating Systems and software configurations Reconnaissance

Decoy Network – DTE0014 Multiple computing resources that can be used for defensive or deceptive purposes Initial Access

Decoy Personna – DTE0015 Used to establish background information about a user. In order to have the adversary believe they are operating against real targets Initial Access, Discovery, Reconnaissance

Decoy System – DTE0017 Computing resources presented to the adversary in support of active defense Reconnaissance

Over the course of this paper, we will discuss some of the widely adapted credential theft attacks executed by adversaries after the initial compromise and then move on to discuss defense techniques against the above MITRE Shield attacks and how to use them effectively to detect deceptive credential usage in the network.

Network Deception – An Active in-network defensive approach

· Most of the targeted attacks involve stealing credentials from the system at a certain point in time as attackers would use them to pivot to other systems in the network. Some of the credential stealing techniques like Golden Ticket attacks have been found to be used in multiple ransomwares armed with lateral movement capabilities.

· Active in-network defense strategies described by the MITRE Shield matrix are significant and play a critical role in detecting credential abuse in the network.

· Network Deception uses these active defense techniques to build the deceptive network infrastructure which could potentially lead to redirecting an attacker’s lateral movement path and engaging them to the decoy services without touching the critical production systems.

· It involves placing decoy systems, decoy credentials and decoy contents all throughout the production network essentially converting it into a trap, playing a crucial role in mitigating the attacks.

McAfee Protection

· McAfee MVISION Endpoint Security has the capabilities to protect against credential theft attacks like credential extraction from LSASS process memory via ATP rule 511. More details on configuring policies and a demo are available here.

· McAfee MVISION Endpoint Detection and Response (EDR) has the capabilities to detect credential access from tools like Mimikatz.

· With McAfee MVISION EDR and ENS integration with Attivo’s network and endpoint deception sensor, McAfee can manage its agents and receive alerts for detections in ePO and EDR.

Lateral Movement – Introduction

Lateral movement refers to the tools and techniques used by attackers to progressively expand their foothold within an enterprise network after gaining initial access. As shown in the figure below, lateral movement activity comprises of several stages starting from credential theft, target enumeration and discovery, privilege escalation, gaining access to network resources and eventually remote code execution on the target before exfiltrating data to accomplish a successful attack. Once inside the network, attackers will deploy a range of techniques at each stage of lateral movement to achieve their end goal. One of the primary challenges an attacker will face while moving laterally inside a network is to hide their activities in plain sight by generating a minimum volume of legitimate looking logs to be able to remain undetected. To achieve this, an attacker might choose to embed the tool within a malicious executable or use the operating system’s internal legitimate tools and services to perform its lateral movement operations, consequently making this network traffic harder to distinguish. As per the Verizon DBIR report 2020, over 80% of data breaches involve credential theft attacks. Credential theft is one of the primary tasks attackers need to perform post-exploitation and after gaining initial control of the target machine. It will usually be the first step towards lateral movement strategies which will allow attackers to elevate their privileges and acquire access to other network resources. As indicated earlier, attackers have long been abusing Windows legitimate features like SMB, RPC over SMB, Windows Management Instrumentation, Windows Remote Management, and many other features to perform lateral movement activities. To remain stealthier, these activities would span a period ranging from many weeks to months.

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