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CAPEC-662: Adversary in the Browser (AiTB)

Attack Pattern ID: 662
Abstraction: Standard
Status: Stable
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+ Description

An adversary exploits security vulnerabilities or inherent functionalities of a web browser, in order to manipulate traffic between two endpoints. This attack first requires the adversary to trick the victim into installing a Trojan Horse application on their system, such as a malicious web browser plugin, which the adversary then leverages to mount the attack. The victim interacts with a web application, such as a banking website, in a normal manner and under the assumption that the connection is secure. However, the adversary can now alter and/or reroute traffic between the client application (e.g., web browser) and the coinciding endpoint, while simultaneously displaying intended transactions and data back to the user. The adversary may also be able to glean cookies, HTTP sessions, and SSL client certificates, which can be used to pivot into an authenticated intranet. Identifying AITB is often difficult because these attacks are successful even when security mechanisms such as SSL/PKI and multifactor authentication are present, since they still function as intended during the attack.

+ Alternate Terms

Term: Man in the Browser

Term: Boy in the Browser

Term: Man in the Mobile

+ Likelihood Of Attack


+ Typical Severity

Very High

+ Relationships
Section HelpThis table shows the other attack patterns and high level categories that are related to this attack pattern. These relationships are defined as ChildOf and ParentOf, and give insight to similar items that may exist at higher and lower levels of abstraction. In addition, relationships such as CanFollow, PeerOf, and CanAlsoBe are defined to show similar attack patterns that the user may want to explore.
ChildOfMeta Attack PatternMeta Attack Pattern - A meta level attack pattern in CAPEC is a decidedly abstract characterization of a specific methodology or technique used in an attack. A meta attack pattern is often void of a specific technology or implementation and is meant to provide an understanding of a high level approach. A meta level attack pattern is a generalization of related group of standard level attack patterns. Meta level attack patterns are particularly useful for architecture and design level threat modeling exercises.94Adversary in the Middle (AiTM)
CanFollowStandard Attack PatternStandard Attack Pattern - A standard level attack pattern in CAPEC is focused on a specific methodology or technique used in an attack. It is often seen as a singular piece of a fully executed attack. A standard attack pattern is meant to provide sufficient details to understand the specific technique and how it attempts to accomplish a desired goal. A standard level attack pattern is a specific type of a more abstract meta level attack pattern.185Malicious Software Download
CanFollowStandard Attack PatternStandard Attack Pattern - A standard level attack pattern in CAPEC is focused on a specific methodology or technique used in an attack. It is often seen as a singular piece of a fully executed attack. A standard attack pattern is meant to provide sufficient details to understand the specific technique and how it attempts to accomplish a desired goal. A standard level attack pattern is a specific type of a more abstract meta level attack pattern.542Targeted Malware
Section HelpThis table shows the views that this attack pattern belongs to and top level categories within that view.
+ Execution Flow
  1. The adversary tricks the victim into installing the Trojan Horse malware onto their system.
    Conduct phishing attacks, drive-by malware installations, or masquerade malicious browser extensions as being legitimate.
  2. The adversary inserts themself into the communication channel initially acting as a routing proxy between the two targeted components.
  1. The adversary observes, filters, or alters passed data of their choosing to gain access to sensitive information or to manipulate the actions of the two target components for their own purposes.
+ Prerequisites
The adversary must install or convince a user to install a Trojan.
There are two components communicating with each other.
An attacker is able to identify the nature and mechanism of communication between the two target components.
Strong mutual authentication is not used between the two target components yielding opportunity for adversarial interposition.
For browser pivoting, the SeDebugPrivilege and a high-integrity process must both exist to execute this attack.
+ Skills Required
[Level: Medium]
Tricking the victim into installing the Trojan is often the most difficult aspect of this attack. Afterwards, the remainder of this attack is fairly trivial.
+ Consequences
Section HelpThis table specifies different individual consequences associated with the attack pattern. The Scope identifies the security property that is violated, while the Impact describes the negative technical impact that arises if an adversary succeeds in their attack. The Likelihood provides information about how likely the specific consequence is expected to be seen relative to the other consequences in the list. For example, there may be high likelihood that a pattern will be used to achieve a certain impact, but a low likelihood that it will be exploited to achieve a different impact.
Modify Data
Access Control
Gain Privileges
Read Data
+ Mitigations
Ensure software and applications are only downloaded from legitimate and reputable sources, in addition to conducting integrity checks on the downloaded component.
Leverage anti-malware tools, which can detect Trojan Horse malware.
Use strong, out-of-band mutual authentication to always fully authenticate both ends of any communications channel.
Limit user permissions to prevent browser pivoting.
Ensure browser sessions are regularly terminated and when their effective lifetime ends.
+ Example Instances

An adversary conducts a phishing attack and tricks a victim into installing a malicious browser plugin. The adversary then positions themself between the victim and their banking institution. The victim begins by initiating a funds transfer from their personal savings to their personal checking account. Using injected JavaScript, the adversary captures this request and modifies it to transfer an increased amount of funds to an account that they controls, before sending it to the bank. The bank processes the transfer and sends the confirmation notice back to the victim, which is instead intercepted by the adversary. The adversary modifies the confirmation to reflect the original transaction details and sends this modified message back to the victim. Upon receiving the confirmation, the victim assumes the transfer was successful and is unaware that their money has just been transferred to the adversary.

In 2020, the Agent Tesla malware was leveraged to conduct AiTB attacks against organizations within the gas, oil, and other energy sectors. The malware was delivered via a spearphishing campaign and has the capability to form-grab, keylog, copy clipboard data, extract credentials, and capture screenshots. [REF-630]

Boy in the browser attacks are a subset of AiTB attacks. Similar to AiTB attacks, the adversary must first trick the victim into installing a Trojan, either via social engineering or drive-by-download attacks. The malware then modifies the victim's "hosts" file in order to reroute web traffic from an intended website to an adversary-controlled website that mimics the legitimate website. The adversary is now able to observe, intercept, and/or modify all traffic, as in a traditional Adversary in the Middle attack (CAPEC-94). BiTB attacks are low-cost, easy to execute, and more difficult to detect since the malware often removes itself once the attack has concluded. [REF-631]

Man in the Mobile attacks are a subset of AiTB attacks that target mobile device users. Like AiTB attacks, an adversary convinces a victim to install a Trojan mobile application on their mobile device, often under the guise of security. Once the victim has installed the application, the adversary can capture all SMS traffic to bypass SMS-based out-of-band authentication systems. [REF-632]

+ Taxonomy Mappings
Relevant to the ATT&CK taxonomy mapping
Entry IDEntry Name
1185Man in the Browser

Relevant to the OWASP taxonomy mapping
Entry Name
Man-in-the-browser attack
+ References
[REF-629] "Man-in-the-browser attack". Open Web Application Security Project (OWASP). <>. URL validated: 2021-02-09.
[REF-630] Liviu Arsene. "Oil and Gas Spearphishing Campaigns Drop Agent Tesla Spyware in Advance of Historic OPEC+ Deal". Bitdefender Labs. 2020-04-21. <>. URL validated: 2021-02-09.
[REF-631] Amit Klein. "Man-in-the-Mobile Attacks Single Out Android". SecurityIntelligence. 2012-07-10. <>. URL validated: 2021-02-10.
[REF-632] Kelly Jackson Higgins. "New 'Boy In The Browser' Attacks On The Rise". Dark Reading, Informa PLC. 2011-02-14. <>. URL validated: 2021-02-10.
+ Content History
Submission DateSubmitterOrganization
2021-06-24CAPEC Content TeamThe MITRE Corporation
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Page Last Updated or Reviewed: October 21, 2021