Avoiding ARP Poisoning Attacks

Defending against ARP Poisoning attacks can be done in numerous ways:

●  Constant ARP Tables

Any and all MAC addresses in a network can be statically mapped to their corresponding IP addresses. It's a great way to stop ARP Poisoning attacks, but it adds a huge amount of extra work for network administrators. Static ARP tables are impractical for most large businesses because of the time and effort required to manually update the ARP tables on all hosts whenever there is a change to the network. However, separating a network segment when static ARP tables are utilized can help to secure sensitive data in instances where security is paramount.

●  Safeguarding Switches

The majority of modern managed Ethernet switches provide protections against ARP Poisoning attacks. These capabilities, which typically go by the name "Dynamic ARP Inspection" (DAI), examine the veracity of each ARP message and discard any packets that look malicious. By default, DAI allows you to set a maximum rate at which ARP messages can be sent through the switch, which effectively protects your network from Denial of Service assaults.

Previously only available on expensive networking equipment, DAI and similar technologies are now standard on nearly all business-grade switches, including those used by smaller enterprises. As a best practice, DAI should be enabled on all ports apart from those directly connected to other switches. There is minimal influence on performance, however the function may need to be activated in tandem with others, such as DHCP Snooping.

ARP Cache Poisoning attacks can be thwarted by turning on Port Security on a switch. Port Security can be used to prevent an attacker from spoofing several network identities by limiting each switch port to a single MAC address.

●  Safety from the Outside

One way to protect against ARP Poisoning attacks is to implement a strict policy for limiting who can enter your building. Due to the fact that ARP messages are not transmitted outside of the local network, any attackers targeting the victim network must be physically close by or already in possession of a machine on the network. It's important to remember that in the case of wireless networks, proximity doesn't necessarily mean that the attacker needs direct physical access; a signal that reaches to a street or parking lot may be adequate. Whether wired or wireless, technologies like 802.1x can help restrict network access to authorized machines.

●  Desertion of Network Connections

Like we've already established, ARP messages don't leave the local subnet. Because an ARP cache poisoning attack on one subnet cannot affect devices on another subnet, a well-segmented network may be less vulnerable to such attacks in general. The potential damage from an ARP Poisoning attack can be considerably mitigated by centralizing critical resources within a separate, secure portion of the network.

●  Encryption

While encryption cannot prevent an ARP attack entirely, it can lessen its impact. Historically, login credentials were often communicated in plain text, making MiTM attacks a popular method for stealing them. SSL/TLS encryption's widespread use has made this kind of cyberattack more challenging. Even if the traffic is intercepted by the threat actor, they will be unable to decrypt it.

●  One of several potential dangers

ARP Poisoning is still a problem today, long after newer threats such as Ransomware had been discovered. It is best dealt with in the same way as any other cyberthreat—via a thorough information security approach. To gain a sense of your company's security status, you can use a tool like Varonis Threat Detection and Response. After an ARP Poisoning attack, Varonis Edge can help identify telltale signals of data exfiltration.

ARP Poisoning: What Is It?

By exploiting ARP's flaws, a malicious actor can poison the MAC addresses assigned to other devices on the network. When ARP was first launched in 1982, security was not a major priority, hence authentication techniques to validate ARP messages were not included. Any network node can respond to an ARP request, regardless of whether or not the message was intended for it. If Computer A "asks" for Computer B's MAC address, an attacker on Computer C can provide it and Computer A will treat it as legitimate. As a result of this error, a number of attacks have become feasible. Using widely available tools, an attacker can "poison" the ARP caches of other computers on a local network by forcing them to store incorrect information.

How to Poison an ARP Receiver

Even while the specifics of an ARP Poisoning assault can change, they always involve at least the following:

1.  The Attacker Picks His/Her Target Machine(s)

An ARP Poisoning attack begins with the selection of a target. A network node might be a single computer, a collection of computers, or a router. One reason why routers are so tempting to attack is that a successful ARP Poisoning Attack against a router can disrupt communications for an entire subnet.

2.  Attacker Launches Tools 

The second step in an ARP Poisoning attack is for the attacker to launch the necessary tools and begin the assault. The attacker will commence the attack after launching the tool of his or her choice and adjusting any relevant settings. They may start sending out ARP messages right away, or they could wait for a request.

3.  Attacker Takes Advantage of the Misdirected Traffic

When an attacker succeeds in corrupting the ARP cache of a victim machine (or machines), they usually do something with the misdirected traffic. They can either examine it, change it, or "blackhole" it so it never reaches its target. How to respond to an attack is conditional on the attacker's goals.