Security Manager's Journal: Closing off a hole in Outlook

In my year and a half or so at my current company, I have slowly built a real security program where none had existed.

I've introduced event management and data leak prevention. We now filter URLs to keep employees off of websites that present security or legal risks to the company. I've introduced two-factor authentication, locked down mobile devices and written and promoted a slew of modern security policies and processes.

Trouble Ticket

Outlook Anywhere makes it possible for users to download email to any device -- and leave sensitive documents on unsafe PCs. Action plan: Restrict the use of Outlook Anywhere to clients that are behind the firewall.

But as I said, this has been a slow process, and I still have a lot of work to do. One neglected area has been email. Email is probably the most vulnerable repository of documents in our company. But it's also the most widely used application and is a huge business enabler, so I've been reluctant to address its security shortcomings head on. After a close call involving some of our intellectual property, however, I can no longer put this off.

We have approved three legitimate ways for employees to access their Exchange mail remotely. The first is via Outlook Web Access (OWA), a Web-based version of the Microsoft Outlook client. I like the fact that OWA mail doesn't reside on the user's computer unless the user takes extra steps to save it locally. And for an additional level of security, I plan to require two-factor authentication for access to OWA.

The second way to obtain email remotely is through ActiveSync, which we use to synchronize email, contacts and calendar information with mobile devices. To enhance security with this option, we push a security policy to all devices that synchronize.

The third way to access email remotely, called Outlook Anywhere and formerly known as RPC over HTTPS, keeps me up at night. With Outlook Anywhere, employees can directly connect their Outlook clients to our Exchange server. It isn't devoid of security features: The connection is secure, and users must enter their network credentials before email can be downloaded to or sent from the client. But once downloaded, any emails, attachments, contacts or calendar items remain on the device, even after the application has been closed. And the device could be anything from a relative's or friend's PC to a computer in a public library or an Internet cafe. That means that sensitive company documents could be lying around on devices accessible by pretty much anyone.

A Close Call

A few weeks ago, the manager of a local hotel called to tell us that the hotel staff had discovered over 1GB of our company email on the computer in the hotel lobby. One of our IT staffers headed over there for a look and found that the email belonged to one of our sales representatives. I told the IT staffer to copy the email to a .pst file and remove it from the hotel computer as best as possible.

We were lucky; this could have turned out much worse. We do a lot of business with that hotel, and the manager, eager to maintain good relations, assured us that the PC would be re-imaged.

A review of the .pst file showed that the sales rep had left behind sensitive corporate data, including information about pending deals and copies of contracts and internal memos, plus a good deal of his own personal information, including some data related to finances.

I now plan to restrict access to Outlook Anywhere to devices located behind our firewall. Remote users will need to sign on to the full-client VPN, and they are allowed to do that only from company-issued PCs. This constitutes a cultural change, so I expect some grumbling, but given the risks involved, I think it's justified as part of my efforts to close serious security holes.

This week's journal is written by a real security manager, "Mathias Thurman," whose name and employer have been disguised for obvious reasons. Contact him at

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