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North Korea-backed hackers have an inspired solution to read your Gmail


SHARPEXT has slurped up a large number of emails during the past year and keeps improving.

North Korea-backed hackers have a clever way to read your Gmail

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Researchers have unearthed never-before-seen malware that hackers from North Korea have already been using to surreptitiously read and download email and attachments from infected users’ Gmail and AOL accounts.

The malware, dubbed SHARPEXT by researchers from security firm Volexity, uses clever methods to use a browser extension for the Chrome and Edge browsers,Volexity reported in a post. The extension can not be detected by the e-mail services, and because the browser was already authenticated using any multifactor authentication protections set up, this ever more popular security measure plays no role in reining in the account compromise.

The malware has been around use for “more than per year,” Volexity said, and may be the work of a hacking group the business tracks as SharpTongue. The group is sponsored by North Korea’s government and overlaps with a group tracked as Kimsuky by other researchers. SHARPEXT is targeting organizations in america, Europe, and South Korea that focus on nuclear weapons along with other issues North Korea deems vital that you its national security.

Volexity President Steven Adair said within an email that the extension gets installed “through spear phishing and social engineering where in fact the victim is fooled into opening a malicious document. Previously we’ve seen DPRK threat actors launch spear phishing attacks where in fact the entire objective was to obtain the victim to set up a browser extension vs it being truly a post exploitation mechanism for persistence and data theft.” In its current incarnation, the malware works only on Windows, but Adair said there is no reason it couldn’t be broadened to infect browsers running on macOS or Linux, too.

Your blog post added: “Volexity’s own visibility shows the extension has been quite successful, as logs obtained by Volexity show the attacker could successfully steal a large number of emails from multiple victims through the malware’s deployment.”

Installing a browser extension throughout a phishing operation minus the end-user noticing isn’t easy. SHARPEXT developers have clearly taken notice of research like what’s published here, here, and here, which ultimately shows what sort of security mechanism in the Chromium browser engine prevents malware from making changes to sensitive user settings. Whenever a legitimate change is manufactured, the browser requires a cryptographic hash of a few of the code. At startup, the browser verifies the hashes, and when some of them don’t match, the browser requests the old settings be restored.

For attackers to work for this protection, they need to first extract the next from the computer they’re compromising:

  • A copy of the resources.pak file from the browser (which provides the HMAC seed utilized by Chrome)
  • The user’s S-ID value
  • The initial Preferences and Secure Preferences files from the user’s system

After modifying the preference files, SHARPEXT automatically loads the extension and executes a PowerShell script that allows DevTools, a setting which allows the browser to perform customized code and settings.

“The script runs within an infinite loop checking for processes linked to the targeted browsers,” Volexity explained. “If any targeted browsers are located running, the script checks the title of the tab for a particular keyword (for instance, ‘05101190,’ or ‘Tab+’ based on the SHARPEXT version). The precise keyword is inserted in to the title by the malicious extension when a dynamic tab changes or whenever a page is loaded.”


The post continued:

The keystrokes sent are equal to Control+Shift+J, the shortcut make it possible for the DevTools panel. Lastly, the PowerShell script hides the newly opened DevTools window utilizing the ShowWindow() API and the SW_HIDE flag. By the end of the process, DevTools is enabled on the active tab, however the window is hidden.

Furthermore, this script can be used to cover up any windows which could alert the victim. Microsoft Edge, for instance, periodically displays a warning message to an individual (Figure 5) if extensions are running in developer mode. The script constantly checks if this window appears and hides it utilizing the ShowWindow() and the SW_HIDE flag.


Once installed, the extension is capable of doing the next requests:

HTTP POST Data Description
mode=list List previously collected email from the victim to make sure duplicates aren’t uploaded. This list is continuously updated as SHARPEXT executes.
mode=domain List email domains with that your victim has previously communicated. This list is continuously updated as SHARPEXT executes.
mode=black Collect a blacklist of email senders that needs to be ignored when collecting email from the victim.
mode=newD&d=[data] Put in a domain to the set of all domains viewed by the victim.
mode=attach&name=[data]&idx=[data]&body=[data] Upload a fresh attachment to the remote server.
mode=new&mid=[data]&mbody=[data] Upload Gmail data to the remote server.
mode=attlist Commented by the attacker; receive an attachments list to be exfiltrated.
mode=new_aol&mid=[data]&mbody=[data] Upload AOL data to the remote server.

SHARPEXT allows the hackers to generate lists of email addresses to ignore also to keep an eye on email or attachments which have recently been stolen.

Volexity created the next summary of the orchestration of the many SHARPEXT components it analyzed:


Your blog post provides images, file names, along with other indicators that trained people may use to determine should they have already been targeted or infected by this malware. The business warned that the threat it poses is continuing to grow as time passes and isn’t more likely to go away anytime soon.

“When Volexity first encountered SHARPEXT, it appeared to be an instrument in early development containing numerous bugs, a sign the tool was immature,” the business said. “The most recent updates and ongoing maintenance demonstrate the attacker is achieving its goals, finding value in continuing to refine it.”

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