Windows 10: Threat

jrowla · Aug 30, 2018

Please advise is this a valid Microsoft response

Hi jrowla,
Microsoft_Support has replied to your question Won't See Email on Desktop but it is on Phone in Microsoft Community.
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Try3 · Aug 31, 2018

Windows defender false positive - forced to allow threat

Windows defender has started to identify C:\Windows\System32\mshta.exe as a threat [normally reported as a Trojan Powessere.G]. I use mshta.exe to run an hta custom MsgBox - I have been hoping to keep using my current CustomMsgBox tool [batch file calling a vbs-hta file] until later this year when I hope to have had enough time to replace it with a PowerShell alternative.

Windows defender's notification lets me "allow the threat" but that seems to me to be a bigger security hole than is necessary - it will now ignore a potentially real intrusion when all I want to run is a genuine Windows component. My immediate problem is fixed but I would prefer to fix the false positive using the exclusions list.

I cleared the 'Allowed threats history' so I could use the exclusions list instead. I added C:\Windows\System32\mshta.exe to the file exclusions list and I checked that it had taken properly by checking the exclusions list both in the UI & in the Registry. But the exclusion made no difference, it continued to detect and block the exe.

I have repeated the attempt several times [by clearing the allowed threats list & exclusions list beforehand] and the results are the same every time
- allowing the threat works,
- using the exclusions list has no effect.

I studied the relevant tutorial but have not spotted an error in what I have been doing - Add or Remove Windows Defender Exclusions

Does anybody with experience of using the exclusions list to counter false positives have any suggestions for me?

Denis

gagagaON · Aug 31, 2018

Is restoring a quarantined threat the same as allowing the threat?

My Windows defender scan reported a threat last week. I quarantined it. After a few days, I updated my defender virus definitions, restored the threat, and ran another scan (because I wanted to find out if it was a false positive). This new scan did not
report any threat.

However, under defender's threat history, allowed items, I see this threat listed. I do NOT want to allow the threat, just wanted to find out if the latest definitions would still reported the file as a threat. How should I do that? Thank you. I am using
windows 10.

Brink · Aug 31, 2018

Microsoft Advanced Threat Analytics - NotPetya malware

On June 27, 2017 reports on a new variant of Petya (which was later referred to as NotPetya) malware infection began spreading across the globe. It seems the malware’s initial infection delivered via the “M.E.doc” update service, a Ukrainian finance application. Based on our investigation so far, the propagation steps executed by the malware can be considered sophisticated and well tested.The malware distributes itself as a DLL file, spreading over internal networks using different lateral movement techniques.

This blog post focuses on the network behavior analysis of NotPetya and the techniques it uses to propagate in the network. This is ongoing research, and we’ll update with additional findings as those become available.

Malware Propagation Flows

Delivery & Initial execution

The malware is delivered via the “M.E.doc” service to infect the first endpoint.

The malware executes and extracts the relevant components to disk. These include:

PsExec – Network remote execution tool.

A credential dumping tool.

More information on these steps can be found at the Windows Security blog.

Reconnaissance

The internal network is probed using multiple discovery methods to identify new workstations and domain controllers. These include:

LANMAN NetServerEnum2 API used to get information about workstations and domain controllers.

Probing using ports 139 and 445 to other endpoints.

If a domain controller is accessible, the malware queries its DHCP Service to enumerate DHCP subnet.

In case DHCP subnets are discovered, the malware will continue its discovery against those subnets as well.

Reconnaissance example – NetServerEnum2

In the screenshot above, we can see the NetServerEnum2 API used by the infected machine.

The response includes the domain controller and a list of all known workstations response.

Lateral Movement

To spread itself on the network, the malware tries to access the administrative share ($admin).

If the SeDebugPrivilege privilege obtained (Step2), a credentials dumping tool is used to recover additional user credentials from the local memory.

Our lab tests have shown that in addition to the current account session, only one additional user is used by the malware to probe the remote hosts. The malware seems to ignore memory dumped users who were tagged under a new credentials session. Moreover, it seems like only one user (the last one who is in memory) is used to probe the destination host

Each target endpoint is accessed using multiple authentication protocols, such as NTLM and Kerberos over GSSAPI (SPNEGO). The credentials used for access are:

Current user context, under which the malware is running.

Successfully dumped credentials (if available).

In the screenshot below, we can see multiple CIFS ticket requests performed by the malware on behalf of the dumped user. Such broad abnormal access attempts performed by the malware will be detected by Microsoft Advanced Threat Analytics’ (ATA) abnormal behavior detection. Based on previously learned user behavior analytics, the detection mechanism will recognize and alert on the abnormal resource access performed by the malware using the compromised credentials.

Multiple TGS-REQ

In the screenshot above, we can see multiple CIFS ticket requests.

Example of abnormal user access – ATA

Remote Execution

If access to the administrative share was obtained, the malware copies itself to the target host and executes PSEXEC and WMIC.

Malware Copy

PSEXEC Service creation

In the screenshot above, the infected host starts executing the PSEXEC tool.

Exploitation (optional)

If all propagation steps failed, the malware tries to execute one of the SMB exploits (MS17-010).

Available SMB Exploits:

EternalBlue – CVE-2017-0144

EternalRomance – CVE-2017-0145

The above steps are performed simultaneously, using multiple threads and runs against each target host. For further information regarding the SMB exploit mitigation, malware encryption steps and initial infection stage, please refer to the Petya worm capabilities blog post.

The spreading capabilities used by the NotPetya malware introduce a new level of sophistication when executing lateral movement.

Detection and mitigation

Microsoft Advanced Threat Analytics allows customers to detect and to investigate a variety of advanced techniques including the lateral movement technique used by NotPetya.

This type of lateral movement can be detected by ATA as abnormal resource access – given the large scanning performed by the user to attempt access additional endpoints on the subnet.

There are several ways customers can detect and prevent NotPetya from impacting their environment.

First, we strongly recommend customers that have not yet installed security update MS17-010 to do so as soon as possible. If applying the patch is not possible, disable SMB V1 on the corporate networks.

Second, we recommend that you verify good credential hygiene. To learn more, read the following article about protecting high value assets with secure admin workstations.

Additional Resources

KB

MS17-010 Security Update

Blog

New ransomware, old techniques: Petya adds worm capabilities

Windows 10 platform resilience against the Petya ransomware attack

Click to expand...

Source: Advanced Threat Analytics security research network technical analysis: NotPetya Microsoft Secure

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