Articles in the series “Exchange forensics: The mysterious case of ghost mail”: [1] [2] [3] [4]

[Note: This is a fiction story, the characters and situations are not real, the only real thing is the technical part, which is based on a mixture of work done, experiences of other colleagues and research carried out. with the same technical dose but with less narrative, you can consult the video of the talk that the author gave at the 11th STIC Conference of the CCN-CERT here]

We return to the investigation of the incident by examining what our colleague had found in the OWA logs. If we gather all the information regarding the accesses made from the two IP addresses with the Firefox User-Agent, we find several patterns of interest:
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Articles in the series “Exchange forensics: The mysterious case of ghost mail”: [1] [2] [3]

[Note: This is a fiction story, the characters and situations are not real, the only real thing is the technical part, which is based on a mixture of work done, experiences of other colleagues and research carried out. with the same technical dose but with less narrative, you can consult the video of the talk that the author gave at the 11th STIC Conference of the CCN-CERT here]

After a sleepless night (tossing and turning, brooding on the incident and trying to understand what may have happened, what we may have overlooked, what we still need to try), we return loaded with caffeine to the Organization.

Autopsy has finished the processing of the hard disk image, but after a superficial analysis of the results our initial theory is confirmed: the user’s computer is clean. In fact, it is so clean that the malicious email did not even touch that computer. Therefore, it is confirmed that everything that happened must have happened in the Exchange.

We keep thinking about the incident, and there is something that irks us: if the attackers had complete control of the Exchange, they could have deleted the mail from the Recoverable Items folder, which they didn’t. But what they did manage was to erase it from the EventHistoryDB table, which operates at a lower level … or perhaps they didn’t either.

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Articles in the series “Exchange forensics: The mysterious case of ghost mail”: [1] [2] [3] [4]

(Note: This is a fiction story, the characters and situations are not real, the only real thing is the technical part, which is based on a mixture of work done, experiences of other colleagues and research carried out. If you want a version with the same technical dose but with less narrative, you can consult the video of the talk that the author gave at the 11th STIC Conference of the CCN-CERT here).

Another day in the office, with a list of pending tasks to plan longer than the beard of Richard Stallman and none of them entertaining: reports, documentation of a couple of projects and the preparation of a meeting is what the menu of the day offers for almost the entire week.
Luckily, the saying that “no plan survives contact with the enemy” in this case works in our favor. The phone rings, and my boss goes straight to the point: “A YARA rule has been triggered from the ATD group in CARMEN of [Redacted] (entity whose identity we are going to leave anonymously, calling it “the Organization” from now on). Take your stuff and rush over there.”

The adrenaline rush at the thrill of the hunt is instantaneous: ATD is our internal name of a group of attackers that we hunted a few months ago on another client, and our reversers ripped the malware open from top to bottom without mercy. The analysis allowed us to detect a series of particular “irregularities” in their way of acting, which allowed us to generate a series of high fidelity YARA rules (that is, false positives practically null). If it was triggered on CARMEN (our advanced intrusion detection tool), then 99% sure to be infected”.
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