ConnectWise, which offers a self-hosted, remote desktop software application that is widely used by Managed Service Providers (MSPs), is warning about an unusually sophisticated phishing attack that can let attackers take remote control over user systems when recipients click the included link. The warning comes just weeks after the company quietly patched a vulnerability that makes it easier for phishers to launch these attacks.
ConnectWise Control is extremely popular among MSPs that manage, protect and service large numbers of computers remotely for client organizations. Their product provides a dynamic software client and hosted server that connects two or more computers together, and provides temporary or persistent remote access to those client systems.
When a support technician wants to use it to remotely administer a computer, the ConnectWise website generates an executable file that is digitally signed by ConnectWise and downloadable by the client via a hyperlink.
When the remote user in need of assistance clicks the link, their computer is then directly connected to the computer of the remote administrator, who can then control the client’s computer as if they were seated in front of it.
While modern Microsoft Windows operating systems by default will ask users whether they want to run a downloaded executable file, many systems set up for remote administration by MSPs disable that user account control feature for this particular application.
In October, security researcher Ken Pyle alerted ConnectWise that their client executable file gets generated based on client-controlled parameters. Meaning, an attacker could craft a ConnectWise Control client download link that would bounce or proxy the remote connection from the MSP’s servers to a server that the attacker controls.
This is dangerous because many organizations that rely on MSPs to manage their computers often set up their networks so that only remote assistance connections coming from their MSP’s networks are allowed.
Using a free ConnectWise trial account, Pyle showed the company how easy it was to create a client executable that is cryptographically signed by ConnectWise and can bypass those network restrictions by bouncing the connection through an attacker’s ConnectWise Control server.
“You as the attacker have full control over the link’s parameters, and that link gets injected into an executable file that is downloaded by the client through an unauthenticated Web interface,” said Pyle, a partner and exploit developer at the security firm Cybir. “I can send this link to a victim, they will click this link, and their workstation will connect back to my instance via a link on your site.”
On Nov. 29, roughly the same time Pyle published a blog post about his findings, ConnectWise issued an advisory warning users to be on guard against a new round email phishing attempts that mimic legitimate email alerts the company sends when it detects unusual activity on a customer account.
“We are aware of a phishing campaign that mimics ConnectWise Control New Login Alert emails and has the potential to lead to unauthorized access to legitimate Control instances,” the company said.
ConnectWise said it released software updates last month that included new protections against the misdirection vulnerability that Pyle reported. But the company said there is no reason to believe the phishers they warned about are exploiting any of the issues reported by Pyle. Continue reading