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Threat Intelligence

3/12/2021
04:30 PM
Kelly Sheridan
Kelly Sheridan
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Microsoft Exchange Server Attacks: 9 Lessons for Defenders

Experts share their guidance for organizations running on-premise Exchange servers in the wake of rapidly spreading attacks.
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A Hot Target to Defend
Microsoft Exchange Server has traditionally been an appealing attack vector, depending on the adversary and their goals, says Joe Slowik, threat researcher with DomainTools. It's an essential component to any organization that uses it, most organizations don't want to take it offline, and there are difficulties with managing it.
'From a non-technical perspective, we have to look at Exchange as being a high availability, high demand sort of service,' he says.
Of course, email isn't limited to inter-employee communications. Email also ties into things like ordering systems, reporting systems, and all sorts of other functionalities. Anything that interferes with the availability of that service is a non-trivial aspect to running most businesses.
'We're talking about an interesting target both for the value it has in itself as a repository of information, including sensitive information in the form of emails, as well as a target that has value as a means to an end because Exchange is going to be able to talk to pretty much every machine in the network,' Slowik explains. 
Exchange server isn't always the final goal for attackers. One already in the target organization may instead go straight for domain admin or similar privileges. While Exchange may be a route toward doing this, most attackers may as well try to dive for the domain controller, Slowik says.
But these Exchange flaws make it easier for an external adversary to gain broad access in a target organization, upping their appeal to attackers -- and the urgency for organizations to act. While Exchange server isn't quite as sensitive as the domain controller, 'it's not terribly far off,' he continues. Getting system privileges on Exchange server can quickly lead to domain admin.
(Image: Alphaspirit -- stock.adobe.com)

A Hot Target to Defend

Microsoft Exchange Server has traditionally been an appealing attack vector, depending on the adversary and their goals, says Joe Slowik, threat researcher with DomainTools. It's an essential component to any organization that uses it, most organizations don't want to take it offline, and there are difficulties with managing it.

"From a non-technical perspective, we have to look at Exchange as being a high availability, high demand sort of service," he says.

Of course, email isn't limited to inter-employee communications. Email also ties into things like ordering systems, reporting systems, and all sorts of other functionalities. Anything that interferes with the availability of that service is a non-trivial aspect to running most businesses.

"We're talking about an interesting target both for the value it has in itself as a repository of information, including sensitive information in the form of emails, as well as a target that has value as a means to an end because Exchange is going to be able to talk to pretty much every machine in the network," Slowik explains.

Exchange server isn't always the final goal for attackers. One already in the target organization may instead go straight for domain admin or similar privileges. While Exchange may be a route toward doing this, most attackers may as well try to dive for the domain controller, Slowik says.

But these Exchange flaws make it easier for an external adversary to gain broad access in a target organization, upping their appeal to attackers -- and the urgency for organizations to act. While Exchange server isn't quite as sensitive as the domain controller, "it's not terribly far off," he continues. Getting system privileges on Exchange server can quickly lead to domain admin.

(Image: Alphaspirit -- stock.adobe.com)

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