Email Bombs Exploit Lax Authentication In Zendesk

Cybercriminals are exploiting weak email authentication settings in Zendesk, using the platform's customer support systems to bombard targets with thousands of spam and harassing messages that appear to come from legitimate companies like The Washington Post, Discord, and NordVPN. KrebsOnSecurity reports: Zendesk is an automated help desk service designed to make it simple for people to contact companies for customer support issues. Earlier this week, KrebsOnSecurity started receiving thousands of ticket creation notification messages through Zendesk in rapid succession, each bearing the name of different Zendesk customers, such as CapCom, CompTIA, Discord, GMAC, NordVPN, The Washington Post, and Tinder.

The abusive missives sent via Zendesk's platform can include any subject line chosen by the abusers. In my case, the messages variously warned about a supposed law enforcement investigation involving KrebsOnSecurity.com, or else contained personal insults. Moreover, the automated messages that are sent out from this type of abuse all come from customer domain names -- not from Zendesk.

In all of the cases above, the messaging abuse would not have been possible if Zendesk customers validated support request email addresses prior to sending responses. Failing to do so may make it easier for Zendesk clients to handle customer support requests, but it also allows ne'er-do-wells to sully the sender's brand in service of disruptive and malicious email floods. 'We recognize that our systems were leveraged against you in a distributed, many-against-one manner,' said Carolyn Camoens, communications director at Zendesk. 'We are actively investigating additional preventive measures. We are also advising customers experiencing this type of activity to follow our general security best practices and configure an authenticated ticket creation workflow.'

Read more of this story at Slashdot.