sessionhijacking

Session hijacking is the unauthorized takeover of a user session, allowing an attacker to impersonate a legitimate user and gain access to the same resources and privileges. It typically centers on obtaining a valid session token, such as a session identifier stored in a cookie or transmitted in a URL, and using that token to continue an ongoing authenticated session.

Attackers can obtain tokens through several vectors. Eavesdropping on unsecured networks can reveal cookies (sidejacking). Malware or credential-stealing software can harvest tokens from a device. Cross-site scripting and insecure server configurations can exfiltrate session data. In some cases, attackers attempt session fixation by steering a user into a known session and then hijacking that session once authentication completes. Man-in-the-middle setups may also intercept and reuse tokens to impersonate the user.

The impact of session hijacking ranges from unauthorized access to personal data, to account takeovers and fraud. It can affect web applications, mobile apps, and any service that relies on persistent session identifiers. Security incidents may erode user trust and can have regulatory and financial consequences, especially where sensitive information is involved.

Defense and prevention focus on protecting session tokens and tightening session management. Transport layer security (HTTPS) with TLS is essential to prevent token exposure in transit. Cookies should be marked Secure and HttpOnly, and SameSite policies can reduce cross-site risks. Token rotation, short session lifetimes, mandatory re-authentication for sensitive actions, and proper logout invalidate sessions. Additional protections include multi-factor authentication, anomaly detection for unusual login patterns, device fingerprinting, and, where feasible, binding sessions to tokens or client certificates. Early detection of suspicious activity and prompt revocation of compromised sessions are critical incident response steps. Historical demonstrations such as the Firesheep incident highlighted the importance of secure transport and cookie protections in mitigating session hijacking.