Steal Web Session Cookie

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.[1]

There are several examples of malware targeting cookies from web browsers on the local system.[2][3] There are also open source frameworks such as Evilginx 2 and Muraena that can gather session cookies through a man-in-the-middle proxy that can be set up by an adversary and used in phishing campaigns.[4][5]

After an adversary acquires a valid cookie, they can then perform a Web Session Cookie technique to login to the corresponding web application.

ID: T1539
Sub-techniques:  No sub-techniques
Platforms: Google Workspace, Linux, Office 365, SaaS, Windows, macOS
Permissions Required: User
Data Sources: File: File Access, Process: Process Access
Contributors: Johann Rehberger; Microsoft Threat Intelligence Center (MSTIC)
Version: 1.1
Created: 08 October 2019
Last Modified: 14 April 2021

Procedure Examples

ID Name Description
S0492 CookieMiner

CookieMiner can steal Google Chrome and Apple Safari browser cookies from the victim’s machine. [6]


EVILNUM can harvest cookies and upload them to the C2 server.[7]

G0120 Evilnum

Evilnum can steal cookies and session information from browsers.[8]

S0531 Grandoreiro

Grandoreiro can steal the victim's cookies to use for duplicating the active session from another device.[9]

S0467 TajMahal

TajMahal has the ability to steal web session cookies from Internet Explorer, Netscape Navigator, FireFox and RealNetworks applications.[2]


ID Mitigation Description
M1032 Multi-factor Authentication

A physical second factor key that uses the target login domain as part of the negotiation protocol will prevent session cookie theft through proxy methods.[10]

M1054 Software Configuration

Configure browsers or tasks to regularly delete persistent cookies.

M1017 User Training

Train users to identify aspects of phishing attempts where they're asked to enter credentials into a site that has the incorrect domain for the application they are logging into.


Monitor for attempts to access files and repositories on a local system that are used to store browser session cookies. Monitor for attempts by programs to inject into or dump browser process memory.