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east-west lateral movement

North-South and East-West Lateral Movement: What’s the Difference?

What are the core concepts of, the differences between, and the ways to mitigate north-south and east-west lateral movement? 

Back when I was knee-high to a Jawa, I was taught a mnemonic trick to remember the points of the compass: “Never Eat Shredded Wheat.” In the UK, at least, it seems everyone has a different way of remembering this, and it can cause much debate around the beer garden table. Youngsters seem to be taught different rhymes to remember the cardinal directions depending on which county they’re from. I’ve heard “Never Eat Soggy Worms,” “Naughty Elephants Squirt Water,” and possibly most divisively, “Never Ever Support Wales.” Thankfully, the difference between north-south and east-west lateral movement is written in stone and nowhere near as regionally contentious. It is, however, one of those things we need to know. 

So what is Lateral Movement Anyway? 

North-south and east-west lateral movement are phrases thrown across Scrum meetings or around the server room, and the core concept refers to the technique used by attackers to navigate through a network after gaining initial access.  

It’s akin to an intruder moving from room to room within an organization’s offices, searching for valuable assets or sensitive information. This movement is typically stealthy and aims to expand the attacker’s foothold by gaining higher privileges or accessing additional systems and resources within the network—like application accounts, requiring service account protection. It’s a critical phase in advanced cyber attacks, often associated with sophisticated threats like Advanced Persistent Threats (APTs).  

“Breaches involving lateral movement tend to be more costly. The average total cost of a data breach in this category was significantly higher than breaches without such movements, partly due to the extended dwell time and broader access obtained by attackers.” [IBM].

Lateral movement cybersecurity is particularly challenging, as this is difficult detect because it often mimics legitimate user activity. Effective network protection against such tactics requires robust perimeter defenses and vigilant monitoring of internal network activities, implementation of strict access controls, and strategies considering the choice between microsegmentation vs. network segmentation—designed to limit the ability of an attacker to move freely across the network, effectively containing the breach and mitigating any potential damage. 

Lateral movement, however, is divided into two distinct concepts: East-west lateral movement and north-south lateral movement. 

What is North-South Lateral Movement? 

North-south lateral movement refers to the movement of data or attackers between the internal network of an organization and the external internet or other networks. This terminology is derived from the typical visualization of network traffic on a diagram, where communications from inside the network (the ‘north’) to the outside internet (the ‘south’) are depicted as moving up and down.  

North-south movement typically involves crossing the network’s perimeter. This could be in the form of an external attack penetrating the network (moving from south to north) or sensitive data being exfiltrated from the internal network to the internet or another external destination (moving from north to south).  

Detecting and preventing north-south lateral movements are crucial for network security. This involves employing robust perimeter defenses like firewalls, intrusion prevention systems (IPS), and advanced threat protection systems that monitor and control the flow of data between the internal network and the external world, as well as implementing stringent access controls and network monitoring to identify and respond to any unauthorized or suspicious activity quickly. 

What is East-West Lateral Movement? 

East-west lateral movement refers to the traffic or the movement of threats within an organization’s internal network. This term originates from the visualization of network traffic where east-west represents the horizontal movement across the network, typically occurring between servers, data centers, applications, and other internal systems.  

In the context of a cyber-attack, east-west lateral movement implies that once an attacker has breached the perimeter defenses (often referred to as North-south movement), they move laterally within the network. This movement is aimed at gaining access to additional resources, escalating privileges, or locating valuable data or assets. It’s a critical part of advanced persistent threats (APTs) and targeted attacks, where attackers aim to remain undetected while they explore the network, often mimicking legitimate user behavior.  

Detecting and mitigating east-west lateral movement is challenging but essential for robust cybersecurity. Traditional perimeter-based defenses are often ineffective against these internal movements. Therefore, strategies like microsegmentation, network segmentation, and advanced internal monitoring and anomaly detection tools are crucial. These approaches limit the ability of an attacker to freely move across the network and access sensitive areas, thereby containing the breach and reducing the potential damage. Additionally, implementing a zero-trust security model, where trust is never assumed and verification is required from anyone attempting to access resources in the network, is becoming increasingly important in defending against east-west lateral movement. 

Different Concepts with Similar Problems 

The difference in concepts is easy to remember once you know. However, just North-south and east-west lateral movements, while distinct in their directional flow within a network, do share several similarities: 

  • Movement of Traffic or Threats: Both terms describe the movement of data or threats within a network. North-south movement pertains to traffic moving between the internal network and the external internet, while east-west movement refers to the traffic or threat progression within the internal network itself.  
  • Security Concerns: Both movements are critical in cybersecurity. North-south movements are often the focus of traditional perimeter security measures, such as firewalls and intrusion detection systems, while east-west movements necessitate internal network security practices like segmentation, access controls, and monitoring. 
  • Pathways for Cyber Attacks: Both can be exploited by cyber attackers. In a north-south scenario, attackers might attempt to penetrate the network from the outside or exfiltrate data to the internet. In east-west scenarios, once inside the network, attackers move laterally to access sensitive information or further compromise systems.  
  • Detection and Monitoring Challenges: Detecting unauthorized or malicious activities in both types of movements is challenging, as attackers often use sophisticated techniques to blend in with normal traffic. Continuous monitoring and advanced security tools are required to identify and respond to potential threats in both scenarios.  
  • Part of Advanced Attack Strategies: In sophisticated cyber-attacks, such as Advanced Persistent Threats (APTs), both types of lateral movements are often used in combination. Attackers may initially penetrate the network (north-south), then move laterally within it (east-west) to reach their objectives.  
  • Need for Comprehensive Security Strategies: Addressing both north-south and east-west movements requires a comprehensive security strategy that encompasses not just perimeter defenses, but also internal network security, segmentation, real-time monitoring, and incident response capabilities.  

While north-south and east-west lateral movement occurs in different planes of a network, they are similar in being pathways for data and threats, presenting significant security challenges, and requiring vigilant monitoring and advanced defense strategies to safeguard network integrity.

A Final Piece of News

While we don’t really need a trick to remember the difference, in closing, I thought I’d give it a go. 

  • N for “North”: Think of “Network Edge”, signifying the movement between the internal network and the external internet or other networks (north-south movement).  
  • E for “East”: Envision “Enterprise Internal”, representing the horizontal, internal traffic within the organization itself (east-west movement).  
  • W for “West”: Also part of “Enterprise Internal”, reinforcing the idea of internal network traffic (east-west movement).  
  • S for “South”: Symbolizes “Security Perimeter Crossing”, indicating the traffic crossing the network’s security perimeter to or from the external environment (north-south movement).  

Yeah, I know, it doesn’t really roll off the tongue. My parents also claimed that the word “News” came from an acronym of North-East-West-South, which, alas it doesn’t, so maybe our version does have some merit after all. 

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