Adversary-in-the-Middle

Adversaries may attempt to position themselves between two or more networked devices using an adversary-in-the-middle (AiTM) technique to support follow-on behaviors such as Network Sniffing, Transmitted Data Manipulation, or replay attacks (Exploitation for Credential Access). By abusing features of common networking protocols that can determine the flow of network traffic (e.g. ARP, DNS, LLMNR, etc.), adversaries may force a device to communicate through an adversary controlled system so they can collect information or perform additional actions.(Citation: Rapid7 MiTM Basics)

For example, adversaries may manipulate victim DNS settings to enable other malicious activities such as preventing/redirecting users from accessing legitimate sites and/or pushing additional malware.(Citation: ttint_rat)(Citation: dns_changer_trojans)(Citation: ad_blocker_with_miner) Adversaries may also manipulate DNS and leverage their position in order to intercept user credentials, including access tokens (Steal Application Access Token) and session cookies (Steal Web Session Cookie).(Citation: volexity_0day_sophos_FW)(Citation: Token tactics) Downgrade Attacks can also be used to establish an AiTM position, such as by negotiating a less secure, deprecated, or weaker version of communication protocol (SSL/TLS) or encryption algorithm.(Citation: mitm_tls_downgrade_att)(Citation: taxonomy_downgrade_att_tls)(Citation: tlseminar_downgrade_att)

Adversaries may also leverage the AiTM position to attempt to monitor and/or modify traffic, such as in Transmitted Data Manipulation. Adversaries can setup a position similar to AiTM to prevent traffic from flowing to the appropriate destination, potentially to Impair Defenses and/or in support of a Network Denial of Service.

Adversaries with privileged network access may seek to modify network traffic in real time using adversary-in-the-middle (AiTM) attacks. (Citation: Gabriel Sanchez October 2017) This type of attack allows the adversary to intercept traffic to and/or from a particular device on the network. If a AiTM attack is established, then the adversary has the ability to block, log, modify, or inject traffic into the communication stream. There are several ways to accomplish this attack, but some of the most-common are Address Resolution Protocol (ARP) poisoning and the use of a proxy. (Citation: Bonnie Zhu, Anthony Joseph, Shankar Sastry 2011)

An AiTM attack may allow an adversary to perform the following attacks:
Block Reporting Message, Spoof Reporting Message, Modify Parameter, Unauthorized Command Message

Adversaries may attempt to position themselves between two or more networked devices to support follow-on behaviors such as Transmitted Data Manipulation or Endpoint Denial of Service.

Adversary-in-the-Middle can be achieved through several mechanisms. For example, a malicious application may register itself as a VPN client, effectively redirecting device traffic to adversary-owned resources. Registering as a VPN client requires user consent on both Android and iOS; additionally, a special entitlement granted by Apple is needed for iOS devices. Alternatively, a malicious application with escalation privileges may utilize those privileges to gain access to network traffic.

Specific to Android devices, adversary-in-the-disk is a type of AiTM attack where adversaries monitor and manipulate data that is exchanged between applications and external storage.(Citation: mitd_kaspersky)(Citation: mitd_checkpoint)(Citation: mitd_checkpoint_research) To accomplish this, a malicious application firsts requests for access to multimedia files on the device (READ_EXTERNAL STORAGE and WRITE_EXTERNAL_STORAGE), then the application reads data on the device and/or writes malware to the device. Though the request for access is common, when used maliciously, adversaries may access files and other sensitive data due to abusing the permission. Multiple applications were shown to be vulnerable against this attack; however, scrutiny of permissions and input validations may mitigate this attack.

Outside of a mobile device, adversaries may be able to capture traffic by employing a rogue base station or Wi-Fi access point. These devices will allow adversaries to capture network traffic after it has left the device, while it is flowing to its destination. On a local network, enterprise techniques could be used, such as ARP Cache Poisoning or DHCP Spoofing.

If applications properly encrypt their network traffic, sensitive data may not be accessible to adversaries, depending on the point of capture. For example, properly implementing Apple’s Application Transport Security (ATS) and Android’s Network Security Configuration (NSC) may prevent sensitive data leaks.(Citation: NSC_Android)