Investigating an “Impossible Travel” Login Alert: A Walkthrough
Updated Published by Kishan Prajapat, SEO & Content Lead
Drafted with Citeya, an AI writing tool built by KPThink.
This is an illustrative scenario, not a report of a real incident. The people, companies, IP addresses (from the ranges reserved for documentation) and figures are made up to show how the investigation works.
A security dashboard raises an “impossible travel” alert: a finance manager signed in from the Chicago office at 9:15 AM, and the same account signed in from Stockholm at 10:30 AM. No one covers that distance in 75 minutes, so either the session has been hijacked or something else explains the location.
Contain while you check
Stolen session cookies let attackers skip multi-factor authentication, so the safe first move is to revoke the account’s active sessions and tokens. That costs the user a sign-in, which is cheap compared with the alternative. Then the investigation can start.
Who owns the Stockholm IP?
The sign-in came from 198.51.100.6. A WHOIS lookup shows the address sits in a block registered to a Swedish hosting company, announced by AS64501. That’s the first clue: a hosting network, not a home broadband or mobile provider, which is where a traveller’s phone or hotel Wi-Fi would normally appear.
A reverse DNS lookup returns a hostname like vpn-se-06.example-vpn.net. Hostnames are set by whoever controls the address, so they’re a hint rather than proof, but this one points strongly at a commercial VPN server.
Confirm with a port scan
A port scan of the IP shows TCP port 443 open and nothing else of note. Many VPN services accept connections on TCP 443 so they work on restrictive networks. The scan can’t confirm WireGuard, which uses UDP port 51820, because a TCP scan doesn’t test UDP at all. Together, though, the hosting network, the hostname and the open port make a VPN endpoint the most likely explanation.
Ask the person
The quickest confirmation is a phone call on a known number, not a message to the possibly compromised account. In this scenario the manager is at their desk in Chicago and had connected to a Swedish VPN server to test a supplier’s website, then forgot to disconnect. False alarm, sessions restored, ticket closed.
The lesson isn’t that impossible-travel alerts are noise. It’s that a few minutes with WHOIS, reverse DNS and a port scan usually tells you whether an IP belongs to a VPN, a hosting provider or a home connection, and that changes what you do next.
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