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Malicious hackers are targeting people in the cryptocurrency space in attacks that start with a link added to the target’s calendar at Calendly, a popular application for scheduling appointments and meetings. The attackers impersonate established cryptocurrency investors and ask to schedule a video conference call. But clicking the meeting link provided by the scammers prompts the user to run a script that quietly installs malware on macOS systems.
KrebsOnSecurity recently heard from a reader who works at a startup that is seeking investment for building a new blockchain platform for the Web. The reader spoke on condition that their name not be used in this story, so for the sake of simplicity we’ll call him Doug.
Being in the cryptocurrency scene, Doug is also active on the instant messenger platform Telegram. Earlier this month, Doug was approached by someone on Telegram whose profile name, image and description said they were Ian Lee, from Signum Capital, a well-established investment firm based in Singapore. The profile also linked to Mr. Lee’s Twitter/X account, which features the same profile image.
The investor expressed interest in financially supporting Doug’s startup, and asked if Doug could find time for a video call to discuss investment prospects. Sure, Doug said, here’s my Calendly profile, book a time and we’ll do it then.
When the day and time of the scheduled meeting with Mr. Lee arrived, Doug clicked the meeting link in his calendar but nothing happened. Doug then messaged the Mr. Lee account on Telegram, who said there was some kind of technology issue with the video platform, and that their IT people suggested using a different meeting link.
Doug clicked the new link, but instead of opening up a videoconference app, a message appeared on his Mac saying the video service was experiencing technical difficulties.
“Some of our users are facing issues with our service,” the message read. “We are actively working on fixing these problems. Please refer to this script as a temporary solution.”
Doug said he ran the script, but nothing appeared to happen after that, and the videoconference application still wouldn’t start. Mr. Lee apologized for the inconvenience and said they would have to reschedule their meeting, but he never responded to any of Doug’s follow-up messages.
It didn’t dawn on Doug until days later that the missed meeting with Mr. Lee might have been a malware attack. Going back to his Telegram client to revisit the conversation, Doug discovered his potential investor had deleted the meeting link and other bits of conversation from their shared chat history.
In a post to its Twitter/X account last month, Signum Capital warned that a fake profile pretending to be their employee Mr. Lee was trying to scam people on Telegram.
The file that Doug ran is a simple Apple Script (file extension “.scpt”) that downloads and executes a malicious trojan made to run on macOS systems. Unfortunately for us, Doug freaked out after deciding he’d been tricked — backing up his important documents, changing his passwords, and then reinstalling macOS on his computer. While this a perfectly sane response, it means we don’t have the actual malware that was pushed to his Mac by the script.
But Doug does still have a copy of the malicious script that was downloaded from clicking the meeting link (the online host serving that link is now offline). A search in Google for a string of text from that script turns up a December 2023 blog post from cryptocurrency security firm SlowMist about phishing attacks on Telegram from North Korean state-sponsored hackers.
“When the project team clicks the link, they encounter a region access restriction,” SlowMist wrote. “At this point, the North Korean hackers coax the team into downloading and running a ‘location-modifying’ malicious script. Once the project team complies, their computer comes under the control of the hackers, leading to the theft of funds.”
Image: SlowMist.
SlowMist says the North Korean phishing scams used the “Add Custom Link” feature of the Calendly meeting scheduling system on event pages to insert malicious links and initiate phishing attacks.
“Since Calendly integrates well with the daily work routines of most project teams, these malicious links do not easily raise suspicion,” the blog post explains. “Consequently, the project teams may inadvertently click on these malicious links, download, and execute malicious code.”
SlowMist said the malware downloaded by the malicious link in their case comes from a North Korean hacking group dubbed “BlueNoroff, which Kaspersky Labs says is a subgroup of the Lazarus hacking group.
“A financially motivated threat actor closely connected with Lazarus that targets banks, casinos, fin-tech companies, POST software and cryptocurrency businesses, and ATMs,” Kaspersky wrote of BlueNoroff in Dec. 2023.
The North Korean regime is known to use stolen cryptocurrencies to fund its military and other state projects. A recent report from Recorded Future finds the Lazarus Group has stolen approximately $3 billion in cryptocurrency over the past six years.
While there is still far more malware out there today targeting Microsoft Windows PCs, the prevalence of information-stealing trojans aimed at macOS users is growing at a steady clip. MacOS computers include X-Protect, Apple’s built-in antivirus technology. But experts say attackers are constantly changing the appearance and behavior of their malware to evade X-Protect.
“Recent updates to macOS’s XProtect signature database indicate that Apple are aware of the problem, but early 2024 has already seen a number of stealer families evade known signatures,” security firm SentinelOne wrote in January.
According to Chris Ueland from the threat hunting platform Hunt.io, the Internet address of the fake meeting website Doug was tricked into visiting (104.168.163,149) hosts or very recently hosted about 75 different domain names, many of which invoke words associated with videoconferencing or cryptocurrency. Those domains indicate this North Korean hacking group is hiding behind a number of phony crypto firms, like the six-month-old website for Cryptowave Capital (cryptowave[.]capital).
In a statement shared with KrebsOnSecurity, Calendly said it was aware of these types of social engineering attacks by cryptocurrency hackers.
“To help prevent these kinds of attacks, our security team and partners have implemented a service to automatically detect fraud and impersonations that could lead to social engineering,” the company said. “We are also actively scanning content for all our customers to catch these types of malicious links and to prevent hackers earlier on. Additionally, we intend to add an interstitial page warning users before they’re redirected away from Calendly to other websites. Along with the steps we’ve taken, we recommend users stay vigilant by keeping their software secure with running the latest updates and verifying suspicious links through tools like VirusTotal to alert them of possible malware. We are continuously strengthening the cybersecurity of our platform to protect our customers.”
The increasing frequency of new Mac malware is a good reminder that Mac users should not depend on security software and tools to flag malicious files, which are frequently bundled with or disguised as legitimate software.
As KrebsOnSecurity has advised Windows users for years, a good rule of safety to live by is this: If you didn’t go looking for it, don’t install it. Following this mantra heads off a great deal of malware attacks, regardless of the platform used. When you do decide to install a piece of software, make sure you are downloading it from the original source, and then keep it updated with any new security fixes.
On that last front, I’ve found it’s a good idea not to wait until the last minute to configure my system before joining a scheduled videoconference call. Even if the call uses software that is already on my computer, it is often the case that software updates are required before the program can be used, and I’m one of those weird people who likes to review any changes to the software maker’s privacy policies or user agreements before choosing to install updates.
Most of all, verify new contacts from strangers before accepting anything from them. In this case, had Doug simply messaged Mr. Lee’s real account on Twitter/X or contacted Signum Capital directly, he would discovered that the real Mr. Lee never asked for a meeting.
If you’re approached in a similar scheme, the response from the would-be victim documented in the SlowMist blog post is probably the best.
Image: SlowMist.
Update: Added comment from Calendly.
The victim shaming site operated by the Snatch ransomware group is leaking data about its true online location and internal operations, as well as the Internet addresses of its visitors, KrebsOnSecurity has found. The leaked data suggest that Snatch is one of several ransomware groups using paid ads on Google.com to trick people into installing malware disguised as popular free software, such as Microsoft Teams, Adobe Reader, Mozilla Thunderbird, and Discord.
First spotted in 2018, the Snatch ransomware group has published data stolen from hundreds of organizations that refused to pay a ransom demand. Snatch publishes its stolen data at a website on the open Internet, and that content is mirrored on the Snatch team’s darknet site, which is only reachable using the global anonymity network Tor.
The victim shaming website for the Snatch ransomware gang.
KrebsOnSecurity has learned that Snatch’s darknet site exposes its “server status” page, which includes information about the true Internet addresses of users accessing the website.
Refreshing this page every few seconds shows that the Snatch darknet site generates a decent amount of traffic, often attracting thousands of visitors each day. But by far the most frequent repeat visitors are coming from Internet addresses in Russia that either currently host Snatch’s clear web domain names or recently did.
The Snatch ransomware gang’s victim shaming site on the darknet is leaking data about its visitors. This “server status” page says that Snatch’s website is on Central European Summer Time (CEST) and is powered by OpenSSL/1.1.1f, which is no longer supported by security updates.
Probably the most active Internet address accessing Snatch’s darknet site is 193.108.114[.]41, which is a server in Yekaterinburg, Russia that hosts several Snatch domains, including snatchteam[.]top, sntech2ch[.]top, dwhyj2[.]top and sn76930193ch[.]top. It could well be that this Internet address is showing up frequently because Snatch’s clear-web site features a toggle button at the top that lets visitors switch over to accessing the site via Tor.
Another Internet address that showed up frequently in the Snatch server status page was 194.168.175[.]226, currently assigned to Matrix Telekom in Russia. According to DomainTools.com, this address also hosts or else recently hosted the usual coterie of Snatch domains, as well as quite a few domains phishing known brands such as Amazon and Cashapp.
The Moscow Internet address 80.66.64[.]15 accessed the Snatch darknet site all day long, and that address also housed the appropriate Snatch clear-web domains. More interestingly, that address is home to multiple recent domains that appear confusingly similar to known software companies, including libreoff1ce[.]com and www-discord[.]com.
This is interesting because the phishing domains associated with the Snatch ransomware gang were all registered to the same Russian name — Mihail Kolesnikov, a name that is somewhat synonymous with recent phishing domains tied to malicious Google ads.
Kolesnikov could be a nod to a Russian general made famous during Boris Yeltsin’s reign. Either way, it’s clearly a pseudonym, but there are some other commonalities among these domains that may provide insight into how Snatch and other ransomware groups are sourcing their victims.
DomainTools says there are more than 1,300 current and former domain names registered to Mihail Kolesnikov between 2013 and July 2023. About half of the domains appear to be older websites advertising female escort services in major cities around the United States (e.g. the now-defunct pittsburghcitygirls[.]com).
The other half of the Kolesnikov websites are far more recent phishing domains mostly ending in “.top” and “.app” that appear designed to mimic the domains of major software companies, including www-citrix[.]top, www-microsofteams[.]top, www-fortinet[.]top, ibreoffice[.]top, www-docker[.]top, www-basecamp[.]top, ccleaner-cdn[.]top, adobeusa[.]top, and www.real-vnc[.]top.
In August 2023, researchers with Trustwave Spiderlabs said they encountered domains registered to Mihail Kolesnikov being used to disseminate the Rilide information stealer trojan.
But it appears multiple crime groups may be using these domains to phish people and disseminate all kinds of information-stealing malware. In February 2023, Spamhaus warned of a huge surge in malicious ads that were hijacking search results in Google.com, and being used to distribute at least five different families of information stealing trojans, including AuroraStealer, IcedID/Bokbot, Meta Stealer, RedLine Stealer and Vidar.
For example, Spamhaus said victims of these malicious ads would search for Microsoft Teams in Google.com, and the search engine would often return a paid ad spoofing Microsoft or Microsoft Teams as the first result — above all other results. The malicious ad would include a logo for Microsoft and at first glance appear to be a safe and trusted place to download the Microsoft Teams client.
However, anyone who clicked on the result was whisked away instead to mlcrosofteams-us[.]top — yet another malicious domain registered to Mr. Kolesnikov. And while visitors to this website may believe they are only downloading the Microsoft Teams client, the installer file includes a copy of the IcedID malware, which is really good at stealing passwords and authentication tokens from the victim’s web browser.
Image: Spamhaus
The founder of the Swiss anti-abuse website abuse.ch told Spamhaus it is likely that some cybercriminals have started to sell “malvertising as a service” on the dark web, and that there is a great deal of demand for this service.
In other words, someone appears to have built a very profitable business churning out and promoting new software-themed phishing domains and selling that as a service to other cybercriminals. Or perhaps they are simply selling any stolen data (and any corporate access) to active and hungry ransomware group affiliates.
The tip about the exposed “server status” page on the Snatch darkweb site came from @htmalgae, the same security researcher who alerted KrebsOnSecurity earlier this month that the darknet victim shaming site run by the 8Base ransomware gang was inadvertently left in development mode.
That oversight revealed not only the true Internet address of the hidden 8Base site (in Russia, naturally), but also the identity of a programmer in Moldova who apparently helped to develop the 8Base code.
@htmalgae said the idea of a ransomware group’s victim shaming site leaking data that they did not intend to expose is deliciously ironic.
“This is a criminal group that shames others for not protecting user data,” @htmalgae said. “And here they are leaking their user data.”
All of the malware mentioned in this story is designed to run on Microsoft Windows devices. But Malwarebytes recently covered the emergence of a Mac-based information stealer trojan called AtomicStealer that was being advertised through malicious Google ads and domains that were confusingly similar to software brands.
Please be extra careful when you are searching online for popular software titles. Cracked, pirated copies of major software titles are a frequent source of infostealer infections, as are these rogue ads masquerading as search results. Make sure to double-check you are actually at the domain you believe you’re visiting *before* you download and install anything.
Stay tuned for Part II of this post, which includes a closer look at the Snatch ransomware group and their founder.
Further reading:
@HTMalgae’s list of the top Internet addresses seen accessing Snatch’s darknet site
Ars Technica: Until Further Notice Think Twice Before Using Google to Download Software
Bleeping Computer: Hackers Abuse Google Ads to Spread Malware in Legit Software
Researchers say mobile malware purveyors have been abusing a bug in the Google Android platform that lets them sneak malicious code into mobile apps and evade security scanning tools. Google says it has updated its app malware detection mechanisms in response to the new research.
At issue is a mobile malware obfuscation method identified by researchers at ThreatFabric, a security firm based in Amsterdam. Aleksandr Eremin, a senior malware analyst at the company, told KrebsOnSecurity they recently encountered a number of mobile banking trojans abusing a bug present in all Android OS versions that involves corrupting components of an app so that its new evil bits will be ignored as invalid by popular mobile security scanning tools, while the app as a whole gets accepted as valid by Android OS and successfully installed.
“There is malware that is patching the .apk file [the app installation file], so that the platform is still treating it as valid and runs all the malicious actions it’s designed to do, while at the same time a lot of tools designed to unpack and decompile these apps fail to process the code,” Eremin explained.
Eremin said ThreatFabric has seen this malware obfuscation method used a few times in the past, but in April 2023 it started finding many more variants of known mobile malware families leveraging it for stealth. The company has since attributed this increase to a semi-automated malware-as-a-service offering in the cybercrime underground that will obfuscate or “crypt” malicious mobile apps for a fee.
Eremin said Google flagged their initial May 9, 2023 report as “high” severity. More recently, Google awarded them a $5,000 bug bounty, even though it did not technically classify their finding as a security vulnerability.
“This was a unique situation in which the reported issue was not classified as a vulnerability and did not impact the Android Open Source Project (AOSP), but did result in an update to our malware detection mechanisms for apps that might try to abuse this issue,” Google said in a written statement.
Google also acknowledged that some of the tools it makes available to developers — including APK Analyzer — currently fail to parse such malicious applications and treat them as invalid, while still allowing them to be installed on user devices.
“We are investigating possible fixes for developer tools and plan to update our documentation accordingly,” Google’s statement continued.
Image: ThreatFabric.
According to ThreatFabric, there are a few telltale signs that app analyzers can look for that may indicate a malicious app is abusing the weakness to masquerade as benign. For starters, they found that apps modified in this way have Android Manifest files that contain newer timestamps than the rest of the files in the software package.
More critically, the Manifest file itself will be changed so that the number of “strings” — plain text in the code, such as comments — specified as present in the app does match the actual number of strings in the software.
One of the mobile malware families known to be abusing this obfuscation method has been dubbed Anatsa, which is a sophisticated Android-based banking trojan that typically is disguised as a harmless application for managing files. Last month, ThreatFabric detailed how the crooks behind Anatsa will purchase older, abandoned file managing apps, or create their own and let the apps build up a considerable user base before updating them with malicious components.
ThreatFabric says Anatsa poses as PDF viewers and other file managing applications because these types of apps already have advanced permissions to remove or modify other files on the host device. The company estimates the people behind Anatsa have delivered more than 30,000 installations of their banking trojan via ongoing Google Play Store malware campaigns.
Google has come under fire in recent months for failing to more proactively police its Play Store for malicious apps, or for once-legitimate applications that later go rogue. This May 2023 story from Ars Technica about a formerly benign screen recording app that turned malicious after garnering 50,000 users notes that Google doesn’t comment when malware is discovered on its platform, beyond thanking the outside researchers who found it and saying the company removes malware as soon as it learns of it.
“The company has never explained what causes its own researchers and automated scanning process to miss malicious apps discovered by outsiders,” Ars’ Dan Goodin wrote. “Google has also been reluctant to actively notify Play users once it learns they were infected by apps promoted and made available by its own service.”
The Ars story mentions one potentially positive change by Google of late: A preventive measure available in Android versions 11 and higher that implements “app hibernation,” which puts apps that have been dormant into a hibernation state that removes their previously granted runtime permissions.
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