How can security teams detect URI Hijacking?

What URI hijacking detection is actually looking for

uri hijacking detection is not just about spotting a bad link. Security teams are looking for evidence that a trusted URI scheme, file type, or handler has been redirected so the wrong application opens attacker-controlled content. The practical signal is a mismatch between the user’s expected destination and the program, handler, or process that actually receives the launch.

This matters because the abuse often sits at the boundary between browser, email client, chat app, and operating system handler registration. A URI that looks ordinary can still trigger the wrong application if custom schemes, default handlers, or protocol associations have been altered. In practice, detection means treating handler state as an asset, not a convenience setting.

Where defenders should look for the trail

Start with the scheme registration and default application state on endpoints. Changes to protocol handlers, unexpected handler replacement, or new custom schemes are often the first indicators that a URI launch path has been manipulated. On managed devices, compare the active handler map against a known-good baseline and pay attention to drift that appears soon after software installs, browser extensions, or persistence activity.

Then correlate those settings with launch context. A suspicious pattern is a URI opened from email, chat, document viewers, or browser content that resolves into an unapproved application or an unexpected command path. The user may report that a link opens the wrong program, but the stronger signal is when that behavior is repeatable across the same scheme or source application. The Mobile App Security Guide is useful here because it covers deep link hijacking, intent interception, scheme squatting, and related launch-path abuse.

Detection is stronger when teams also inspect installation and configuration events around the same time window. Newly registered handlers, altered association files, registry or preference changes, and execution spawned through unusual parent processes all help distinguish accidental misrouting from deliberate hijack behavior. The key question is whether the handler state changed before the abnormal launch pattern began.

How to reduce false positives and confirm abuse

Not every wrong-program launch is a security incident. Some are caused by broken associations, missing software, or legitimate user customization. Analysts should confirm whether the affected scheme is approved, whether the target application is expected, and whether the launch path is consistent across multiple users or only on one host. If the same handler deviation appears on more than one endpoint, the likelihood of a broader configuration or abuse issue rises quickly.

It also helps to look for user or application reports that describe links opening the wrong program after a recent install, update, or profile change. That context often separates a harmless association problem from a hijack that is being used to steer users into an attacker-controlled application or payload. When the launch path is untrusted, the issue is not only misconfiguration, but the trust boundary itself. For endpoint monitoring and response context, SANS Security Resources is a practical reference for detection and incident handling patterns.

Risk and Threat Considerations

URI hijacking is risky because it abuses a trusted user action, opening a link, to route execution into software the user did not intend to trust. That can expose credentials, trigger malicious content, or create a foothold through a handler that the user assumes is normal. The attacker goal is usually to convert routine link handling into a reliable execution path.

Failure mechanism: A malicious or altered handler registration replaces the expected destination for a scheme, so a trusted link launches attacker-controlled code, a phishing surface, or an unintended application path instead of the legitimate handler.

Impact: Users can be redirected into credential theft, payload delivery, session abuse, or persistence through protocol associations, and defenders may miss the abuse if they only inspect the visible URL rather than the handler resolution path.

Practitioner Guidance

What to verify: Validate the current handler map on managed endpoints against an approved baseline, especially for custom schemes, browser associations, and enterprise line-of-business protocols. Treat unexplained handler drift as a security event when it coincides with new software, browser changes, or repeated user complaints.

What to prioritise: Focus first on schemes that can launch privileged or high-trust applications, because those create the greatest blast radius. If a malicious or unknown handler can receive mail, chat, or browser traffic, contain that path before spending time on low-risk cosmetic association issues.

Practitioner takeaway: The most useful signal is not merely that a link opened, but that the trust relationship behind the handler changed. Security teams should baseline handler state, watch for drift, and investigate any URI path that resolves into software the user and platform did not intend.

Related resources from NHI Mgmt Group

• Why are NHIs a critical concern for security teams?
• What steps should security teams take to prevent Shadow AI risks?
• Why is the abuse of NHIs a priority for security teams?
• What is the difference between SAST and DAST for security teams?