Menaces liées aux vols de cookies et contre-mesures

### Executive summary This ANSSI guidance explains how stolen web session cookies are exploited by both cybercriminals and strategic threat actors to impersonate users, bypass MFA, access cloud services and administrative interfaces—illustrated with cases involving LAPSUS$, OKTA/EA compromises, and NOBELIUM/StellarParticle activity—and describes mitigations including session lifetime reduction, reauthentication for sensitive actions, detection of session hijacking, and administrative workstation hardening.