Cybercriminals are abusing a widespread lack of authentication within the customer support platform Zendesk to flood focused electronic mail inboxes with menacing messages that come from a whole bunch of Zendesk company clients concurrently.
Zendesk is an automatic assist desk service designed to make it easy for individuals to contact corporations for buyer help points. Earlier this week, KrebsOnSecurity began receiving 1000’s of ticket creation notification messages via Zendesk in speedy succession, every bearing the identify of various Zendesk clients, similar to CapCom, CompTIA, Discord, GMAC, NordVPN, The Washington Submit, and Tinder.
The abusive missives despatched through Zendesk’s platform can embody any topic line chosen by the abusers. In my case, the messages variously warned a couple of supposed legislation enforcement investigation involving KrebsOnSecurity.com, or else contained private insults.
Furthermore, the automated messages which might be despatched out from this kind of abuse all come from buyer domains — not from Zendesk. Within the instance beneath, replying to any of the junk buyer help responses from The Washington Submit’s Zendesk set up reveals the reply-to deal with is assist@washpost.com.
One among dozens of messages despatched to me this week by The Washington Submit.
Notified concerning the mass abuse of their platform, Zendesk stated the emails have been ticket creation notifications from buyer accounts that configured their Zendesk occasion to permit anybody to submit help requests — together with nameless customers.
“A lot of these help tickets might be a part of a buyer’s workflow, the place a previous verification isn’t required to permit them to interact and make use of the Assist capabilities,” stated Carolyn Camoens, communications director at Zendesk. “Though we advocate our clients to allow solely verified customers to submit tickets, some Zendesk clients choose to make use of an nameless atmosphere to permit for tickets to be created on account of varied enterprise causes.”
Camoens stated requests that may be submitted in an nameless method can even make use of an electronic mail deal with of the submitter’s selection.
“Nonetheless, this technique can be used for spam requests to be created on behalf of third celebration electronic mail addresses,” Camoens stated. “If an account has enabled the auto-responder set off based mostly on ticket creation, then this permits for the ticket notification electronic mail to be despatched from our buyer’s accounts to those third events. The notification can even embody the Topic added by the creator of those tickets.”
Zendesk claims it makes use of fee limits to stop a excessive quantity of requests from being created without delay, however these limits didn’t cease Zendesk clients from flooding my inbox with 1000’s of messages in only a few hours.
“We acknowledge that our programs have been leveraged towards you in a distributed, many-against-one method,” Camoens stated. “We’re actively investigating further preventive measures. We’re additionally advising clients experiencing this kind of exercise to observe our normal safety greatest practices and configure an authenticated ticket creation workflow.”
In all the instances above, the messaging abuse wouldn’t have been attainable if Zendesk clients validated help request electronic mail addresses previous to sending responses. Failing to take action could make it simpler for Zendesk shoppers to deal with buyer help requests, however it additionally permits ne’er-do-wells to sully the sender’s model in service of disruptive and malicious electronic mail floods.
