Monthly Archives: May 2020

Windows malware Sarwent got an upgrade. Thou shalt not work with permanent administrative privileges!

23 May 2020

Catalin Cimpanu (1) reports in his post „Windows malware opens RDP ports on PCs for future remote access“ published on ZDNET that the Windows malware Sarwent got an upgrade: It is now capable of using the windows command line and PowerShell, adding users, and opening ports in the Windows firewall for RDP access from remote. Since the latter features require administrative privileges on the victims machine, it is very likely that the victims worked with permanent administrative privileges.

To mitigate the risk, the best approach is to revoke any administrative privileges from standard users. This will not reduce the likelihood of occurrence, but it will reduce the severity of impact of an infection with Sarwent. Furthermore, since the attacker is forced to download tools to fully compromise the victims computer, the likelihood of detectability is increased.

Revoking administrative privileges from standard users is a low-cost, high-impact means to enhance resiliency against cyber-attacks, thus should be part of each security strategy.

But it is hard to implement. Managers will face lots of discussions if users must give up beloved habits. It is very important to keep the number of exceptions as small as possible because every exception lowers the overall security level of the company.

Have a great weekend.


  1. Cimpanu C. Windows malware opens RDP ports on PCs for future remote access [Internet]. ZDNet. 2020 [zitiert 22. Mai 2020]. Verfügbar unter: https://www.zdnet.com/article/windows-malware-opens-rdp-ports-on-pcs-for-future-remote-access/

Thunderspy – Don‘t panic!

19 May 2020

Björn Ruytenberg‘s (1) publication about 7 vulnerabilities in Intel’s Thunderbolt interface justifiably attracts a lot of media attention. Ruytenberg writes in the summary:

“Thunderspy targets devices with a Thunderbolt port. If your computer has such a port, an attacker who gets brief physical access to it can read and copy all your data, even if your drive is encrypted and your computer is locked or set to sleep.”

In Nazmus Sakib’s (2) post in the Microsoft Security Blog this sounds more dramatically:

“An attacker with physical access to a system can use Thunderspy to read and copy data even from systems that have encryption with password protection enabled.”

For the record: Full Disk Encryption (FDE) like BitLocker or LUKS only protects against theft if the computer is in shutdown or hibernation mode. In these cases, the system asks for the passphrase to encrypt the device. If the computer is booted or in sleep mode full disk encryption is useless.

This also holds for Thunderspy. The facts in brief. Thunderspy is a classic “evil maid DMA” attack. The attacker has to flash the Thunderbolt firmware with malicious code and wait for the victim to boot his computer. Once the computer is left unattended the attacker plugs in a specially crafted Thunderbolt device and copies data from the disk.

This is nothing new. The bad news is that all Thunderbolt-equipped computers built between 2011 and 2020 are affected. And that the vulnerabilities cannot be fixed; a hardware redesign is required.

So, everyone with a Thunderbolt-equipped computer should be concerned? No, absolutely not.

Risk for Consumers
The risk for consumers is unchanged because, in general, these devices are not secured, neither with a BIOS password nor with FDE, thus easy to compromise, e.g., with a Linux Live System, if left unattended.

Risk for Business people
The risk for business people is slightly increased. Business computers in general are secured with FDE, so the attacker must wait until the computer is left unattended to plug in the malicious device. Mitigation in this case requires a change in our habits: Put the computer in hibernation mode, instead in sleep mode, if you leave you workplace. The other important rule, “Don’t attach unknown devices to your computer” is already followed in the business domain.

Risk for Executives
The risk for business executives, military, government officials, etc. is unchanged. This group is always under attack, thus hopefully well protected.

Picture credit: Setreset (1)

Picture credit: Setreset (1)

Dan Goodin (3) sums it up:

“Readers who are left wondering how big a threat Thunderspy poses should remember that the high bar of this attack makes it highly unlikely it will ever be actively used in real-world settings, except, perhaps, for the highest-value targets coveted by secretive spy agencies. Whichever camp has a better case, nothing will change that reality.”

Don’t panic!


References

  1. Ruytenberg B. Thunderspy – When Lightning Strikes Thrice: Breaking Thunderbolt 3 Security [Internet]. Thunderspy. 2020 [zitiert 18. Mai 2020]. Verfügbar unter: https://thunderspy.io/
  2. Sakib N. Secured-core PCs help customers stay ahead of advanced data theft [Internet]. Microsoft Security Blog. 2020 [zitiert 18. Mai 2020]. Verfügbar unter: https://www.microsoft.com/security/blog/2020/05/13/secured-core-pcs-help-customers-stay-ahead-of-advanced-data-theft/
  3. Goodin D. Thunderspy: What it is, why it’s not scary, and what to do about it [Internet]. Ars Technica. 2020 [zitiert 13. Mai 2020]. Verfügbar unter: https://arstechnica.com/information-technology/2020/05/thunderspy-what-is-is-why-its-not-scary-and-what-to-do-about-it/

PIcture credit

  1. Setreset / CC BY-SA (https://creativecommons.org/licenses/by-sa/3.0), https://commons.wikimedia.org/wiki/File:Spy_silhouette.svg

Have you patched these top 10 routinely exploited vulnerabilities?

16 May 2020

On Tuesday, CISA published the alert (AA20-133A) on the „Top 10 Routinely Exploited Vulnerabilities“(1). A day later, Zeljka Zorz raised the absolutely legitimate question „Have you patched these top 10 routinely exploited vulnerabilities?“(2) on HELPNETSECURITY.

A query against the NIST NVD and the Exploit-DB shows a gloomy picture:

Top 10 Exploited Vulnerabilities

Top 10 Exploited Vulnerabilities

For the red highlighted vulnerabilities the exploit was available at the day of publication in the NVD. For the green highlighted vulnerabilities the exploit was published shortly after the vulnerability. So, the question should be:

How fast did you patch these top 10 routinely exploited vulnerabilities?

These are telling examples and they are not isolated:

Exploit Publication Date relative to CVE Publication Date

Exploit Publication Date relative to CVE Publication Date

The data from 2013 – 2019 for critical vulnerabilities show:

  • 41% of exploits were published before or at the same day the CVE was published, and
  • 43% of Exploits were published in the range between 10 days before and 10 days after the CVE.

Time is crucial in cyber space operations. In high risk domains, critical vulnerabilities should be patched at least 24 hours after the patch is available. If a vendor cannot provide a patch in time mitigting measures should be applied, in the worst case, systems must be removed from the internet.

Remind the Equifax case (CVE-2017-5638) from 2017.

Have a good weekend.


References

  1. CISA. Top 10 Routinely Exploited Vulnerabilities [Internet]. National Cyber Awareness System. 2020 [zitiert 16. Mai 2020]. Verfügbar unter: https://www.us-cert.gov/ncas/alerts/aa20-133a

  2. Zorz Z. Have you patched these top 10 routinely exploited vulnerabilities? [Internet]. Help Net Security. 2020 [zitiert 14. Mai 2020]. Verfügbar unter: https://www.helpnetsecurity.com/2020/05/13/routinely-exploited-vulnerabilities/