Cookie Stealers Explained: How Hackers Use Them and Why They’re Dangerous
Cookie stealers are malware designed to steal session cookies, allowing attackers to access victims' accounts without requiring a password. This attack method is commonly used to compromise social media, banking services, and accounts on other platforms.
In this article, i will break down how cookie stealers work, and why they pose a significant risk to online security.
First of all: what are cookies?
Cookies are small pieces of data stored by a web browser when a user visits a website. They serve various purposes, such as remembering login sessions, storing user preferences, and tracking browsing activity. Websites use cookies to enhance user experience, but they can also be exploited by attackers, especially in session hijacking attacks.
Types of Cookies
There are several types of cookies, but the most relevant are:
Session Cookies: these are temporary cookies that store session data while a user is active on a website. They are deleted once the browser is closed.
Persistent Cookies: these remain on the device even after closing the browser, allowing websites to remember login details and preferences over multiple sessions. A lot of sites, like Google and Amazon, use this type of cookies.
Secure Cookies: cookies that can only be transmitted over encrypted HTTPS connections to prevent interception.
HttpOnly Cookies – Restricted from client-side scripts, making them less vulnerable to cross-site scripting (XSS) attacks.
What Are Session Cookies?
Session cookies are used to maintain user authentication during a browsing session. When you log into a website, the server generates a unique session ID and stores it in a session cookie on your browser. This session ID verifies your identity for every request you make, so you don’t need to re-enter credentials on every page. Very useful and convenient, right?
Since session cookies expire when the browser is closed, they are commonly used for temporary authentication rather than persistent logins. However, attackers can steal session cookies while they are active, allowing them to hijack user accounts without needing a password.
Now the interesting part: How they steal these cookies?
There are various techniques hackers use to steal session and persistent cookies. The most common are:
Session Hijacking – Attackers intercept a valid session cookie, usually by doing a MitM (Man-in-the-Middle) attack, and use it to gain unauthorized access to an account.
Cookie Stealers – Malware designed to extract session cookies from a browser’s database or memory, and they are very common, especially in cracked games or apps.
Cross-Site Scripting (XSS) – Injecting malicious scripts into websites to steal cookies from unsuspecting users.
Malicious Browser Extensions – Some extensions access and send session cookies to attackers, but it requires the extension to be approved to the browser add-on store, so it’s fairly rare.
Why Session Cookies Are a Security Risk?
As i wrote before, if an hacker steal your session cookies, he can login without a password. The real risk arises when the cookie is a persistent cookie: since they don’t get deleted even after closing the browser, attackers have an increased attack window. Another problem is that traditional security measures focus on credentials, not active sessions, making cookie theft harder to detect. Last, but not for importance, cookies are used on every site that requires authentication (online banking, social media accounts and so on), making them valuable targets.
“Is there a way to protect my cookies?”, you may ask.
Yes, there is a way to protect your cookies:
Use Secure Websites. Always log in through HTTPS to prevent cookies from being intercepted.
Enable Multi-Factor Authentication (MFA) – Some platforms detect stolen cookies and require re-authentication (and honestly, i advise you to really activate it. If a site lets you enable MFA, enable it. In case your account is stolen, you have more chances of getting it back).
Clear Cookies Regularly – Even though it’s a nuisance, reducing stored session cookies minimizes the risk of them being stolen.
Monitor Account Activity – Check for unauthorized logins and terminate suspicious sessions, if they are listed.
Disable Third-Party Cookies – Reduces exposure to tracking and potential cookie theft.
Use Encrypted Storage – Some browsers encrypt cookies to prevent malware from extracting them (Firefox, doesn’t encrypt your cookies. Other browser maybe, but i am sure Firefox doesn’t).
Conclusions:
I advise people and friends to never click on shady links (it’s pretty obvious no one is generous enough to gift you a 50$ amazon gift card, right?), to always install software and drivers from trusted sources (GitHub is a good source, just make sure to check the developer’s other repositories and the source code of the software/driver you need.)
