Case Study: Thwarting a Major Phishing Attack with DNS Filtering

A mid-sized financial services firm received a coordinated phishing campaign targeting 200+ employees over a 48-hour period. The emails impersonated a legitimate vendor and contained links to a convincing login page hosted on a newly registered domain that mimicked the vendor's branding. Traditional email security allowed several emails through because the sending infrastructure had no prior reputation.

Twelve employees clicked the link. On networks without DNS security, clicking the link would load the phishing page, credentials would be entered, and the attacker would gain access to the vendor portal — and potentially pivot to internal systems using the same credentials. The attack would succeed silently, discovered only when the attacker used the stolen credentials days later.

Securd's Greywall intervened at the DNS layer. The phishing domain had been registered 6 hours before the campaign began. It had never been queried by any endpoint in the organization. When the first employee clicked the link and their browser attempted to resolve the domain, Securd's Greywall held the query. The employee saw a block page instead of the phishing site. No credentials were exposed.

The Securd dashboard immediately showed the held domain with 12 unique endpoint queries — revealing the scope of the campaign within minutes. The security team blocked the domain permanently, exported the affected endpoint list for follow-up, and notified the impersonated vendor. Total time from first click to complete containment: 8 minutes. Total credentials compromised: zero.

Without DNS-layer protection, this scenario plays out differently. Even with email security filtering most of the phishing emails, the few that get through succeed — because once a user clicks the link, there's nothing between the browser and the phishing page. DNS security adds the critical last layer: even if the email gets through, even if the user clicks, the malicious domain doesn't resolve.