Kerberos that authenticates cleanly — and stays secure.
When Kerberos breaks, it fails in confusing ways: intermittent logins, apps that silently fall back to NTLM, the dreaded SSPI error. We find the root cause — SPNs, delegation, or time — fix it, and close the security gaps attackers look for.
Find the root cause, not the symptom.
Kerberos is the authentication backbone of Active Directory — and when it misbehaves, the error messages rarely point at the real problem. A missing service principal name sends everything falling back to NTLM. A ten-minute clock difference throws KRB_AP_ERR_SKEW. A service account misconfigured for delegation quietly breaks the "double hop" so a web app can't reach the database behind it.
We diagnose the whole ticket flow — SPNs, delegation, encryption types, and time sync — and fix the actual cause. Then we harden it: service accounts are a favorite target, so we close the doors to Kerberoasting and delegation abuse while we're in there.
Where Kerberos actually breaks.
Six root causes account for the overwhelming majority of Kerberos tickets. We work through them methodically.
SPNs & NTLM fallback
Missing or duplicate service principal names are the top cause of failures — auth silently falls back to NTLM or dies with Cannot generate SSPI context. We audit and correct them.
Delegation & the double hop
Unconstrained, constrained, and resource-based constrained delegation (RBCD) configured correctly, so a front-end service can act on a user's behalf to a back-end — without opening a security hole.
Time & encryption
Kerberos fails past ~5 minutes of clock skew. We fix time sync and resolve encryption-type mismatches — moving service accounts off legacy RC4 to AES.
Entra Kerberos & hybrid
Microsoft Entra Kerberos for hybrid identities — enabling passwordless sign-in and Kerberos for Azure Files without a line of sight to a domain controller.
Service-account hardening
Service accounts with weak passwords are the target of Kerberoasting. We move you to group managed service accounts (gMSA) and strong, rotated credentials.
Attack-path review
We check for the exposures that turn a Kerberos misconfig into a breach — AS-REP roasting, over-privileged delegation, and the conditions that enable golden/silver-ticket attacks.
Recognize any of these?
These are the tickets that get escalated to us — the ones that don't resolve with a reboot.
- "Cannot generate SSPI context" errors
- Intermittent or random authentication failures
- Apps silently falling back to NTLM
- Delegation / double-hop not working
- Clock-skew authentication errors
- Service accounts exposed to Kerberoasting
Kerberos, answered.
Why do I get "Cannot generate SSPI context"?
Almost always a service principal name (SPN) problem — the SPN is missing, registered on the wrong account, or duplicated across two accounts. Kerberos can't find a valid ticket target, so authentication fails. We audit the SPNs, remove duplicates, and register them on the correct service account.
What is an SPN and why does it matter?
A service principal name uniquely identifies a service instance so Kerberos knows which account to issue a ticket for. If it's wrong or missing, Kerberos can't authenticate the service and the client falls back to NTLM — or fails outright. Correct SPNs are the foundation of Kerberos working at all.
What is Kerberoasting, and am I exposed?
Kerberoasting is an attack where a foothold on the network is used to request service tickets and crack them offline to recover weak service-account passwords. If you have service accounts with weak passwords and SPNs, you're exposed. We reduce the risk with gMSA, strong credentials, and AES encryption.
Chasing a Kerberos problem that won't stay fixed?
Send us the error and a bit of context. We'll trace it to the real cause — and harden things while we're there.