Each month, we publish a review that covers essential activities of the last 30 days. This month, we talk about coronavirus-related news, Let’s Encrypt’s certificate revocation, new attacks on hardware, issues with Tor Browser, and more.
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News of the month
In March 2020, we read the following reports:
2019–20 coronavirus pandemic
Of course, the entire world talks about the current pandemic these days. Giving any medical advice is out-of-scope of our blog. Follow the instructions of your national public health authorities, help people in need, and stay healthy (easier said than done).
In the digital world, different groups milk the topic for their interests. Criminals drop malware on faked virus maps, large organizations offer their services (temporarily) for free, and smaller groups try to convince people to use their “alternatives.” The goal is to either hack you or get new customers.
Be aware of such activities. Check links sent by your family and friends, as usual. Think twice before you register new accounts or use new services. Look for missing or incomplete privacy policies (read “GDPR: How to identify incomplete privacy policies?”). Keep in mind that so-called “alternatives” aren’t necessarily better for your privacy and may expose lots of your personal data on the server. Don’t act with precipitation.
We generally recommend that you read our post “Tips for your cyber hygiene”, which we published last October.
Let’s Encrypt’s certificate revocation
In February, Let’s Encrypt (a widely-known non-profit certificate authority) announced that they issued their billionth certificate. Several days later, they found a bug in their CAA code. CAA means “Certification Authority Authorization.” CAA is part of the server-side DNS configuration and tells certificate authorities if they are authorized to issue certificates for a given domain name (read our article on “Server-side DNS security configuration”).
Due to the bug, Let’s Encrypt didn’t check CAA records within 8 hours before the issuance of a new certificate. This check is mandatory for CAs. Therefore, Let’s Encrypt decided to revoke more than 3 million certificates in early March. Later, Let’s Encrypt only revoked 1.7 million certificates, and decided that revoking more could be disruptive to web users. The investigation showed that Let’s Encrypt issued 445 certificates despite CAA records that forbid the issuance.
We think this again shows that all of us heavily depend on the security of certificate authorities. Large parts of web security can be compromised if CAs fail to comply with standards.
New attacks on hardware
In March, security researchers announced several further attacks on hardware:
- “Take A Way: Exploring the Security Implications of AMD’s Cache Way Predictors” describes new side-channel attacks affecting AMD CPUs from 2011 to 2019. The attacks (Collide+Probe and Load+Reload) exploit the L1D cache way predictor to access secret information. Interestingly, AMD stated that these aren’t new attacks in any way.
- In the case of Intel, researches presented the Meltdown-based (and theoretical) “Load Value Injection” attack. Intel released firmware updates that fix the vulnerability. The researches stated that the attack could also affect other CPUs.
- Finally, “TRRespass” was titled “Return of the Rowhammer attack”. Researches showed that most current DRAM modules are vulnerable to this attack, esp. DDR4 and LPDDR4.
In general, it is a good indication that researchers uncover more and more hardware vulnerabilities. It is also a good sign when hardware manufacturers timely provide security updates. When you choose hardware, keep in mind that many attacks on Intel CPUs, AMD CPUs, and other hardware components are purely theoretical. Numerous of these security vulnerabilities are either hard to exploit or can only be exploited locally (the attacker has to be in the same place as the CPU). Other attacks are only relevant for hosting companies when multiple virtual server instances share the same physical CPU.
Firefox 74.0: The death and revival of TLS 1.0 and 1.1
Mozilla published Firefox 74.0 in March. As previously announced, they disabled TLS 1.0 and 1.1 by default. TLS 1.0 and 1.1 are widely considered insecure and shouldn’t be used. However, there are still web servers and web applications that don’t support TLS 1.2 or 1.3. Due to the current pandemic, Mozilla re-enabled TLS 1.0 and 1.1 for an indefinite period.
If you don’t need TLS 1.0 and 1.1, you can manually disable it by changing the configuration of your Firefox. In Firefox, go to
about:config. Click “Accept the Risk and Continue.” Search for
security.tls.version.min and set it to
3 means “TLS 1.2”,
4 means “TLS 1.3”. While using TLS 1.3 is the most secure option, many web servers and web applications don’t support it at the moment.
Besides, Mozilla announced to disable FTP (File Transfer Protocol) in Firefox 77.
Further, the updated version of HTTPS Everywhere introduced the EASE (Encrypt All Sites Eligible) mode. The developers of the Tor Browser explicitly state that you shouldn’t enable EASE as this can be used to identify you.
Data breaches and leaks
Moreover, there were some data breaches and leaks. Have I Been Pwned added information about the following breaches and leaks:
- AnimeGame (breached in February 2020)
- The Halloween Spot (breached in September 2019)
- PropTiger (breached in January 2018)
- Tamodo (breached in February 2020)
- Dueling Network (breached in March 2017)
Tool of the month
This time, we briefly look at USBGuard. USBGuard is a Linux-only framework that protects a system against malicious USB devices. The current version is 0.7.6, released in November 2019. USBGuard should be in the repositories of most Linux distributions. Usually, it isn’t installed since non-technical users can be confused by this tool.
USBGuard is handy when your system is in an exposed environment. For instance, somebody could connect their USB drive with an unattended or public computer. One option is to remove or disable exposed USB ports physically. However, this solution becomes impractical if you need the USB ports for legitimate USB devices. USBGuard can be used to create an allowlist of authorized USB devices.
After installation, you must enable the USBGuard service. In your terminal, enter
sudo systemctl start usbguard and
sudo systemctl enable usbguard. All USB devices that are currently connected to the machine are allowed by default. The initial allowlist includes internal USB devices!
In your terminal, enter
usbguard list-devices to see all USB devices that are connected to the system.
If you connect another USB device to the machine, it is blocked by default. Enter
usbguard list-devices -b. The new device should be listed. You can enter
usbguard allow-device [id] to allow the device. Moreover, you can enter
usbguard block-device [id] to block an authorized device on the allowlist.
USBGuard allows you to define rules specific to USB ports of your machine. You can also set user- or group-specific rules. We may cover this in an upcoming article.
Our activities of the month
In March, we published one article:
- Social engineering: The story of Jessika: We gave another lecture on social engineering for Master students. This time, the students had to invade the privacy of the fictional character Jessika to exploit her.
Besides, we changed several things on our blog:
- We started to improve the style, grammar, and wording of our articles. You can call it spring cleaning.
- We added a link to key.openpgp.org as another mirror for retrieving our current OpenPGP key.
Follow us on Mastodon:
As mentioned last month, we are currently busy. We publish security news in the Fediverse as usual (feel free to subscribe to our RSS/Atom feed, or directly follow us in the Fediverse). We expect to return to a “normal” state in April 2020.
- Let's Encrypt: Revoking certain certificates on March 4external link
- Let’s Encrypt changes course on certificate revocationexternal link
- Take A Way: Exploring the Security Implications of AMD's Cache Way Predictorsexternal link (PDF file)
- LVI - Hijacking Transient Execution with Load Value Injectionexternal link
- TRRespassexternal link
- Firefox 74.0 release notesexternal link
- USBGuardexternal link