T1539: Steal Web Session Cookie

Credential Access Intelligence Profile

AI Answer

An adversary may steal web application or service session cookies and use them to gain access to web applications or Internet services as an authenticated user without needing credentials. Web applications and services often use session cookies as an authentication token after a user has authenticated to a website. Cookies are often valid for an (Source: MITRE ATT&CK T1539)

Confidence: 0.9 · Source: MITRE ATT&CK · Requires review: yes · Freshness: 2026-09-07

ATT&CK Mapping

Field	Value
Technique ID	T1539
Name	Steal Web Session Cookie
Tactic	Credential Access (credential-access)
Platforms	Linux, macOS, Office Suite, SaaS, Windows
Sub-technique	No

Why it matters

In the OpenTrojan knowledge graph, Steal Web Session Cookie (T1539) is one of the highest-connectivity ATT&CK techniques: 29 MITRE STIX relationships reference this technique; 8 threat groups observed using it; 20 software families associated; 1 campaigns associated. These counts are derived from MITRE ATT&CK STIX relationships and are not an estimate of exploitation volume.

How attackers use it

Behavior described below is from the MITRE ATT&CK canonical definition (source: https://attack.mitre.org/techniques/T1539). An adversary may steal web application or service session cookies and use them to gain access to web applications or Internet services as an authenticated user without needing credentials. Web applications and services often use session cookies as an authentication token after a user has authenticated to a website. Cookies are often valid for an extended period of time, even if the web application is not actively used. Cookies can be found on disk, in the process memory of the browser, and in network traffic to remote systems. Additionally, other applications on the targets machine might store sensitive authentication cookies in memory (e.g. apps which authenticate to cloud services). Session cookies can be used to bypasses some multi-factor authentication protocols. There are several examples of malware targeting cookies from web browsers on the local system. Adversaries may also steal cookies by injecting malicious JavaScript content into websites or relying on User Execution by tricking victims into running malicious JavaScript in their browser. There are also open source frameworks such as Evilginx2 and Muraena that can gather session cookies through a malicious proxy (e.g., Adversary-in-the-Middle) that can be set up by an adversary and used in phishing campaigns. After an adversary acquires a valid cookie, they can then perform a Web Session Cookie technique to login to the corresponding web application.

Detection

Not available — MITRE ATT&CK does not currently publish a structured detection strategy for this technique in the ingested dataset.

Mitigation

Restricting web-based content involves enforcing policies and technologies that limit access to potentially malicious websites, unsafe downloads, and unauthorized browser behaviors. This can include URL filtering, download restrictions, script blocking, and extension control to protect against exploitation, phishing, and malware delivery. This mitigation can be implemented through the following measures:

Deploy Web Proxy Filtering:

Use solutions to filter web traffic based on categories, reputation, and content types.
Enforce policies that block unsafe websites or file types at the gateway level.

Enable DNS-Based Filtering:

Implement tools to restrict access to domains associated with malware or phishing campaigns.
Use public DNS filtering services to enhance protection.

Enforce Content Security Policies (CSP):

Configure CSP headers on internal and external web applications to restrict script execution, iframe embedding, and cross-origin requests.

Control Browser Features:

Disable unapproved browser features like automatic downloads, developer tools, or unsafe scripting.
Enforce policies through tools like Group Policy Management to control browser settings.

Monitor and Alert on Web-Based Threats:

Use SIEM tools to collect and analyze web proxy logs for signs of anomalous or malicious activity.
Configure alerts for access attempts to blocked domains or repeated file download failures.

Mitigation guidance is from the MITRE ATT&CK course-of-action associated with this technique.

TRANSLATEXT
Lumma Stealer
DarkGate
Chaes
LODEINFO
EVILNUM
GlassWorm
Spica
BLUELIGHT
RedLine Stealer
Grandoreiro
XLoader

Software associations are from MITRE ATT&CK STIX relationships (observed usage, not attribution).

Kimsuky
Evilnum
Sandworm Team
Scattered Spider
Lotus Blossom
Star Blizzard
LuminousMoth
APT42

Group associations are from MITRE ATT&CK STIX relationships.

SolarWinds Compromise

Campaign associations are from MITRE ATT&CK STIX relationships.

References

Source Attribution

Source: MITRE ATT&CK (MITRE ATT&CK) · Confidence: 0.9 · Reviewed: OpenTrojan - Human Review

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Evidence — assertions mapped to verifiable references.
Timeline — events in chronological order.
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Sources — NVD, CISA KEV, MITRE ATT&CK, vendor advisories.
Notes — your own observations and working hypotheses.

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