Mar 21 2018

Citrix Releases Security Updates

Original release date: March 21, 2018

Citrix has released security updates to address vulnerabilities in its XenServer. A remote attacker could exploit some of these vulnerabilities to take control of an affected system.

NCCIC/US-CERT encourages users and administrators to review the Citrix Security Bulletin CTX232655 and apply the necessary updates.

This product is provided subject to this Notification and this Privacy & Use policy.

Mar 20 2018

AMD promises firmware fixes for security processor bugs

Enlarge / AMD's Ryzen die. Threadripper has two of these in a multi-chip module. Epyc has four of them. (credit: AMD)

AMD has responded to the reports last week of a range of security flaws affecting its Platform Security Processor (PSP) and chipset. The company acknowledges the bugs and says that, in coming weeks, it will have new firmware available to resolve the PSP bugs. These firmware fixes will also mitigate the chipset bugs.

Israeli firm CTS identified four separate flaw families, naming them Masterkey (affecting Ryzen and Epyc processors), Ryzenfall (affecting Ryzen, Ryzen Pro, and Ryzen Mobile), Fallout (hitting only Epyc), and Chimera (applying to Ryzen and Ryzen Pro systems using the Promonotory chipset).

Masterkey, Ryzenfall, and Fallout are all problems affecting the Platform Security Processor (PSP), a small ARM core that's integrated into the chips to provide certain additional features such as a firmware-based TPM security module. The PSP has its own firmware and operating system that runs independently of the main x86 CPU. Software running on the x86 CPU can access PSP functionality using a device driver, though this access is restricted to administrator/root-level accounts.

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Mar 20 2018

Krebs on Security 2018-03-20 13:19:11

A 15-year-old security researcher has discovered a serious flaw in cryptocurrency hardware wallets made by Ledger, a French company whose popular products are designed to physically safeguard public and private keys used to receive or spend the user’s cryptocurrencies.

Ledger’s Nano-S cryptocurrency hardware wallet. Source: Amazon.

Hardware wallets like those sold by Ledger are designed to protect the user’s private keys from malicious software that might try to harvest those credentials from the user’s computer.  The devices enable transactions via a connection to a USB port on the user’s computer, but they don’t reveal the private key to the PC.

Yet Saleem Rashid, a 15-year-old security researcher from the United Kingdom, discovered a way to acquire the private keys from Ledger devices. Rashid’s method requires an attacker to have physical access to the device, and normally such hacks would be unremarkable because they fall under the #1 rule of security — namely, if an attacker has physical access to your device, then it is not your device anymore.

The trouble is that consumer demand for Ledger’s products has frequently outpaced the company’s ability to produce them (it has sold over a million of its most popular Nano S models to date). This has prompted the company’s chief technology officer to state publicly that Ledger’s built-in security model is so robust that it is safe to purchase their products from a wide range of third-party sellers, including Amazon and eBay.

Ledger’s message to users regarding the lack of anti-tampering mechanisms on its cryptocurrency hardware wallets.

But Rashid discovered that a reseller of Ledger’s products could update the devices with malicious code that would lie in wait for a potential buyer to use it, and then siphon the private key and drain the user’s cryptocurrency account(s) when the user goes to use it.

The crux of the problem is that Ledger’s devices contain a secure processor chip and a non-secure microcontroller chip. The latter is used for a variety of non-security related purposes, from handling the USB connections to displaying text on the Ledger’s digital display, but the two chips still pass information between each other. Rashid found that an attacker could compromise the insecure processor (the microcontroller) on Ledger devices to run malicious code without being detected.

Ledger’s products do contain a mechanism for checking to ensure the code powering the devices has not been modified, but Rashid’s proof-of-concept code — being released today in tandem with an announcement from Ledger about a new firmware update designed to fix the bug — allows an attacker to force the device to sidestep those security checks.

“You’re essentially trusting a non-secure chip not to change what’s displayed on the screen or change what the buttons are saying,” Rashid said in an interview with KrebsOnSecurity. “You can install whatever you want on that non-secure chip, because the code running on there can lie to you.”

Kenneth White, director of the Open Crypto Audit Project, had an opportunity to review Rashid’s findings prior to their publication today. White said he was impressed with the elegance of the proof-of-concept attack code, which Rashid sent to Ledger approximately four months ago. A copy of Rashid’s research paper on the vulnerability is available here (PDF). A video of Rashid demonstrating his attack is below.

White said Rashid’s code subverts the security of the Ledger’s process for generating a backup code for a user’s private key, which relies on a random number generator that can be made to produce non-random results.

“In this case [the attacker] can set it to whatever he wants,” White said. “The victim generates keys and backup codes, but in fact those codes have been predicted by the attacker in advance because he controls the Ledger’s random number generator.”

Rashid said Ledger initially dismissed his findings as implausible. But in a blog post published today, Ledger says it has since fixed the flaw Rashid found — as well as others discovered and reported by different security researchers — in a firmware update that brings Ledger Nano S devices from firmware version 1.3.1 to version 1.4.1 (the company actually released the firmware update on March 6, potentially giving attackers time to reverse engineer Rashid’s method).

The company is still working on an update for its pricier Ledger Blue devices, which company chief security officer Charles Guillemet said should be ready soon. Guillemet said Nano-S devices should alert users that a firmware update is available when the customer first plugs the device into a computer.

“The vulnerability he found was based on the fact that the secure element tries to authenticate the microcontroller, and that authentication is not strong enough,” Guillemet told KrebsOnSecurity. “This update does authentication more tightly so that it’s not possible to fool the user.”

Rashid said unlike its competitors in the hardware wallet industry, Ledger includes no tamper protection seal or any other device that might warn customers that a Nano S has been physically opened or modified prior to its first use by the customer.

“They make it so easy to open the device that you can take your fingernail and open it up,” he said.

Asked whether Ledger intends to add tamper protection to its products, Guillemet said such mechanisms do not add any security.

“For us, a tamper proof seal is nothing that adds security to the device because it’s very easy to counterfeit,” Guillemet said. “You can buy some security seals on the web. For us, it’s a lie to our customers to use this kind of seal to prove the genuineness of our product.”

Guillemet said despite Rashid’s findings, he sees no reason to change his recommendation that interested customers should feel free to purchase the company’s products through third party vendors.

“As we have upgraded our solution to prove the genuineness of our product using cryptographic checks, I don’t see why we should change this statement,” he said.

Nevertheless, given that many cryptocurrency owners turn to hardware wallets like Ledger to safeguard some or all of their virtual currency, it’s probably a good idea if you are going to rely on one of these devices to purchase it directly from the source, and to apply any available firmware updates before using it.

Mar 19 2018

Ransomware Takes Open-Source Path, Encrypts With GNU Privacy Guard

McAfee Labs has recently observed a new variant of ransomware that relies on the open-source program GNU Privacy Guard (GnuPG) to encrypt data. GnuPG is a hybrid-encryption software program that uses a combination of conventional symmetric-key cryptography for speed and public-key cryptography to ease the secure key exchange. Although ransomware using GnuPG to encrypt files is not unique, it is uncommon.

We analyzed the following SHA-256 hashes of the malware GPGQwerty:

  • 2762a7eadb782d8a404ad033144954384be3ed11e9714c468c99f0d3df644ef5
  • 39c510bc504a647ef8fa1da8ad3a34755a762f1be48e200b9ae558a41841e502
  • f5cd435ea9a1c9b7ec374ccbd08cc6c4ea866bcdc438ea8f1523251966c6e88b

We found these hashes need many support files for successful execution. The three files themselves will not encrypt anything. GPGQwerty consists of a bundle of files that runs together to encrypt a victim’s machine. The bundle comprises ten files:

This ransomware was first seen at the beginning of March. Generally, this type of malware spreads by spam email, malicious attachments, exploits, or fraudulent downloads. The binary 39c510bc504a647ef8fa1da8ad3a34755a762f1be48e200b9ae558a41841e502 was spotted in the wild at hxxp://; it may be part of a drive-by download strategy or was hosted on a legitimate site.

Key.bat, run.js, and find.exe are three files that play a vital role in the encryption process. The infection process follows this path:


The binary find.exe has eight sections and the raw size of its .bss section is zero.

It also has an unusual time and date stamp:

The file includes malicious thread local storage (TLS) callbacks as an anti-analysis trick. Generally, this technique allows executable files to include malicious TLS callback functions to run prior to the AddressOfEntryPoint field (the normal execution point of a binary) in the executable header.

The action starts with the execution of the batch file key.bat. It imports the key and launches find.exe on the victim’s machine by executing the JavaScript run.js. The contents of the batch and JavaScript files are shown in the following snippet:

This ransomware kills some selected running tasks using command-line utility taskkill. This command has options to kill a task or process either by using the process ID or the image filename. In the following snippet, we see it terminating some processes forcefully by using their image names.

The ransomware tries to encrypt data using GnuPG (gpg.exe). The malware appends the extension .qwerty to the encrypted files:

The malware overwrites the original files using shred.exe:

After encryption, the ransomware allots a unique ID that identifies each victim. It also creates a .txt file that states all files on the computer have been locked and the victim must pay to decrypt the files.

GPGQwerty deletes the recycle bin using the Windows utility del:

Using the command “vssadmin.exe Delete Shadows /All /Quiet,” the ransomware silently removes the volume shadow copies (vssadmin.exe, wmic.exe) from the target’s system, thus preventing the victim from restoring the encrypted files. It also deletes backup catalogs (wbadmin.exe) and disables automatic repair at boot time (bcdedit.exe):

Finally, it creates the ransom note readme_decrypt.txt in each folder that holds an encrypted file. The ransom note gives instructions to communicate with an email address within 72 hours to arrange payment.

This Yara rule detects GPGQwerty:

rule crime_ransomware_windows_GPGQwerty: crime_ransomware_windows_GPGQwerty



author = “McAfee Labs”

description = “Detect GPGQwerty ransomware”


$a = “gpg.exe –recipient qwerty  -o”

$b = “%s%s.%d.qwerty”

$c = “del /Q /F /S %s$recycle.bin”

$d = “”


          all of them



McAfee advises all users to keep their antimalware products up to date. McAfee products detect this malware as Ransomware-GKF! [Partial hash] with DAT Versions 8826 and later. For more on combatin

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