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If you operate a cybercrime business that relies on disseminating malicious software, you probably also spend a good deal of time trying to disguise or “crypt” your malware so that it appears benign to antivirus and security products. In fact, the process of “crypting” malware is sufficiently complex and time-consuming that most serious cybercrooks will outsource this critical function to a handful of trusted third parties. This story explores the history and identity behind Cryptor[.]biz, a long-running crypting service that is trusted by some of the biggest names in cybercrime.
Virtually all malware that is deployed for use in data stealing at some point needs to be crypted. This highly technical, laborious process involves iteratively altering the appearance and behavior of a malicious file until it no longer sets off alarm bells when scanned by different antivirus tools.
Experienced malware purveyors understand that if they’re not continuously crypting their malware before sending it out, then a lot more of whatever digital disease they are trying to spread is going to get flagged by security tools. In short, if you are running a cybercrime enterprise and you’re not equipped to handle this crypting process yourself, you probably need to pay someone else to do it for you.
Thanks to the high demand for reliable crypting services, there are countless cybercriminals who’ve hung out their shingles as crypting service providers. However, most of these people do not appear to be very good at what they do, because most are soon out of business.
One standout is Cryptor[.]biz. This service is actually recommended by the purveyors of the RedLine information stealer malware, which is a popular and powerful malware kit that specializes in stealing victim data and is often used to lay the groundwork for ransomware attacks. Cryptor[.]biz also has been recommended to customers of the Vidar information stealer malware family (via the malware’s Telegram support channels).
As good as Cryptor[.]biz may be at obfuscating malware, its proprietor does not appear to have done a great job covering his own tracks. The registration records for the website Cryptor[.]biz are hidden behind privacy protection services, but the site’s homepage says potential customers should register by visiting the domain crypt[.]guru, or by sending a Jabber instant message to the address “masscrypt@exploit.im.”
Crypt[.]guru’s registration records also are hidden, yet passive domain name system (DNS) records for both cryptor[.]biz and crypt[.]guru show that in 2018 the domains were forwarding incoming email to the address obelisk57@gmail.com.
Cyber intelligence firm Intel 471 reports that obelisk57@gmail.com was used to register an account on the forum Blacksoftware under the nickname “Kerens.” Meanwhile, the Jabber address masscrypt@exploit.im has been associated with the user Kerens on the Russian hacking forum Exploit from 2011 to the present day.
The login page for Cryptor dot biz contains several clues about who runs the service.
The very first post by Kerens on Exploit in 2011 was a negative review of a popular crypting service that predated Cryptor[.]biz called VIP Crypt, which Kerens accused of being “shitty” and unreliable. But Intel 471 finds that after his critical review of VIP Crypt, Kerens did not post publicly on Exploit again for another four years until October 2016, when they suddenly began advertising Cryptor[.]biz.
Intel 471 found that Kerens used the email address pepyak@gmail.com, which also was used to register Kerens accounts on the Russian language hacking forums Verified and Damagelab.
Ironically, Verified has itself been hacked multiple times over the years, with its private messages and user registration details leaked online. Those records indicate the user Kerens registered on Verified in March 2009 from an Internet address in Novosibirsk, a city in the southern Siberian region of Russia.
In 2010, someone with the username Pepyak on the Russian language affiliate forum GoFuckBiz[.]com shared that they typically split their time during the year between living in Siberia (during the milder months) and Thailand (when Novosibirsk is typically -15 °C/°5F).
For example, in one conversation about the best car to buy for navigating shoddy roads, Pepyak declared, “We have shitty roads in Siberia.” In January 2010, Pepyak asked the GoFuckBiz community where one might find a good USB-based modem in Phuket, Thailand.
DomainTools.com says the email address pepyak@gmail.com was used to register 28 domain names over the years, including a now-defunct Russian automobile sales website called “autodoska[.]biz.” DomainTools shows this website was registered in 2008 to a Yuri Churnov from Sevastpol, Crimea (prior to Russia’s annexation of Crimea in 2014, the peninsula was part of Ukraine).
The WHOIS records for autodoska[.]biz were changed in 2010 to Sergey Purtov (pepyak@gmail.com) from Yurga, a town in Russia’s Kemerovo Oblast, which is a relatively populous area in Western Siberia that is adjacent to Novosibirsk.
A satellite view of the region including Novosibirsk, Yurga and Kemerovo Oblast. Image: Google Maps.
Many of the 28 domains registered to pepyak@gmail.com have another email address in their registration records: unforgiven57@mail.ru. According to DomainTools, the Unforgiven email address was used to register roughly a dozen domains, including three that were originally registered to Keren’s email address — pepyak@gmail.com (e.g., antivirusxp09[.]com).
One of the domains registered in 2006 to the address unforgiven57@mail.ru was thelib[.]ru, which for many years was a place to download pirated e-books. DomainTools says thelib[.]ru was originally registered to a Sergey U Purtov.
Most of the two-dozen domains registered to pepyak@gmail.com shared a server at one point with a small number of other domains, including mobile-soft[.]su, which was registered to the email address spurtov@gmail.com.
CDEK, an express delivery company based in Novosibirsk, was apparently hacked at some point because cyber intelligence firm Constella Intelligence found that its database shows the email address spurtov@gmail.com was assigned to a Sergey Yurievich Purtov (Сергей Юрьевич Пуртов).
DomainTools says the same phone number in the registration records for autodoska[.]biz (+7.9235059268) was used to secure two other domains — bile[.]ru and thelibrary[.]ru, both of which were registered to a Sergey Y Purtov.
A search on the phone number 79235059268 in Skype reveals these digits belong to a “Sergey” from Novosibirsk with the now-familiar username — Pepyak.
Bringing things full circle, Constella Intelligence shows that various online accounts tied to the email address unforgiven57@mail.ru frequently relied on the somewhat unique password, “plk139t51z.” Constella says that same password was used for just a handful of other email addresses, including gumboldt@gmail.com.
Hacked customer records from CDEK show gumboldt@gmail.com was tied to a customer named Sergey Yurievich Purtov. DomainTools found that virtually all of the 15 domain names registered to gumboldt@gmail.com (including the aforementioned mobile-soft[.]su) were at one point registered to spurtov@gmail.com.
Intel 471 reports that gumboldt@gmail.com was used in 2009 to register a user by the nickname “Kolumb” on the Russian hacking forum Antichat. From Kolumb’s posts on Antichat, it seems this user was mostly interested in buying access to compromised computers inside of Russia.
Then in December 2009, Kolumb said they were in desperate need of a reliable crypting service or full-time cryptor.
“We need a person who will crypt software every day, sometimes even a couple of times a day,” Kolumb wrote on Antichat.
Mr. Purtov did not respond to requests for comment sent to any of the email addresses referenced in this report. Mail.ru responded that the email address spurtov@mail.ru is no longer active.
As KrebsOnSecurity opined on Mastodon earlier this week, it makes a lot of sense for cybersecurity researchers and law enforcement alike to focus attention on the top players in the crypting space — for several reasons. Most critically, the cybercriminals offering time-tested crypting services also tend to be among the most experienced and connected malicious coders on the planet.
Think of it this way: By definition, a crypting service scans and examines all types of malware before those new nasties are first set loose in the wild. This fact alone should make these criminal enterprises a primary target of cybersecurity firms looking to gain more timely intelligence about new malware.
Also, a review of countless posts and private messages from Pepyak and other crypting providers shows that a successful crypting service will have direct and frequent contact with some of the world’s most advanced malware authors.
In short, infiltrating or disrupting a trusted crypting service can be an excellent way to slow down or even sideline a large number of cybercrime operations all at once.
Further reading on the crypting industry:
This Service Helps Malware Authors Fix Flaws in Their Code
Antivirus is Dead: Long Live Antivirus!
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Explore the nature of vulnerabilities in this episode of ThreatWise TV.
It’s shaping up to be another big year for vulnerability disclosure. Already the number of Common Vulnerabilities and Exposures (CVEs) disclosed has crossed 18,000 and it’s on track to make this another record-breaking year.
With new CVEs being disclosed daily, it has become increasingly difficult for security teams to stay abreast of the latest risks, let alone quickly determine which ones apply to their network environment. From those, prioritizing which CVEs to patch first adds an additional wrinkle to the process.
If this wasn’t challenging enough, a curve ball that’s often lobbed at security teams are the “breaking news” vulnerabilities— vulnerabilities picked up by the security media, often with much fanfare. The stories surrounding these high-profile vulnerabilities generally carry an implied threat that the CVE in question will throw the doors wide open to attackers if not addressed immediately. What security team hasn’t had someone from the C-suite share an article they’ve read, asking “are we protected from this?”
On the surface, CVEs that appear severe enough to garner media attention do seem like a good place to start when addressing vulnerabilities in your environment. But vulnerabilities are complicated, and what a security researcher manages to do within a controlled environment doesn’t always translate into real-world attacks. In fact, most disclosed vulnerabilities never see active exploitation. And of those that do, not every vulnerability ends up becoming a tool in an attacker’s arsenal. Bad actors generally follow the path of least resistance when they compromise a network, relying on tested exploits long before trying something new and unproven.
This begs the question: how much overlap is there between the most talked about vulnerabilities and those that are widely used in attacks? Moreover, if media attention isn’t a reliable indicator, what else might predict if a vulnerability will be used in an attack?
To answer these questions, we used intelligence tools available from Cisco’s Kenna Security risk-based vulnerability management (RBVM) software. In particular, Kenna.VI+ consolidates a variety of vulnerability intelligence, where a CVE ID lookup can pull back a wealth of information. In addition to this, Kenna.VI+ includes an API that brings in an additional layer of external threat intelligence, enabling further analysis.
We started with a direct comparison of Successful Exploitations and Chatter Count from within Kenna.VI+. The former is a full count of confirmed exploits within the dataset, while the latter is a count of mentions in the news, social media, various forums, and the dark web.
Our first pass at the data included a comparison of the top 50 CVEs in both Successful Exploitations and Chatter Count. However, there were only two CVEs that overlapped. The data showed that many of the top exploited CVEs were old and predated the data in Chatter Count. We quickly decided that this wasn’t a fair comparison.
To get a better look at more relevant CVEs, we limited the dataset to a range of 10 years. Unfortunately, this did not do much to improve things—only three CVEs showed up in both lists.
A more effective approach was to look at CVEs that we know are actively being exploited. The Cybersecurity and Infrastructure Security Agency (CISA) happens to maintain such a list. The Known Exploited Vulnerabilities (KEV) catalog is considered an authoritative compilation of vulnerabilities identified as being actively exploited in the wild.
Running the KEV catalog though Kenna.VI+ resulted in six CVEs that appeared in the top 50 for both lists, with a single overlap in the top 10. This leads us to conclude that the vulnerabilities with the most discussion are not the same as those being actively exploited in the majority of cases.
| CVE | Brief description | |
| 1 | CVE-2017-9841 | PHPUnit vulnerability (used to target popular CMSes) |
| 2 | CVE-2021-44228 | Log4j vulnerability |
| 3 | CVE-2019-0703 | Windows SMB information disclosure vulnerability |
| 4 | CVE-2014-0160 | Heartbleed vulnerability |
| 5 | CVE-2017-9805 | REST plugin in Apache Struts vulnerability |
| 6 | CVE-2017-11882 | Microsoft Office memory corruption vulnerability |
| 7 | CVE-2017-5638 | Apache Struts vulnerability (used in Equifax breach) |
| 8 | CVE-2012-1823 | 10-year-old PHP vulnerability |
| 9 | CVE-2017-0144 | EternalBlue vulnerability |
| 10 | CVE-2018-11776 | Apache Struts RCE vulnerability |
| CVE | Brief description | |
| 1 | CVE-2021-26855 | Microsoft Exchange vulnerability (used in Hafnium attacks) |
| 2 | CVE-2021-40444 | Microsoft MSHTML RCE vulnerability |
| 3 | CVE-2021-26084 | Confluence Server and Data Center vulnerability |
| 4 | CVE-2021-27065 | Microsoft Exchange vulnerability (used in Hafnium attacks) |
| 5 | CVE-2021-34473 | Microsoft Exchange vulnerability (used in Hafnium attacks) |
| 6 | CVE-2021-26858 | Microsoft Exchange vulnerability (used in Hafnium attacks) |
| 7 | CVE-2021-44228 | Log4j vulnerability |
| 8 | CVE-2021-34527 | One of the PrintNightmare vulnerabilities |
| 9 | CVE-2021-41773 | Apache HTTP Server vulnerability |
| 10 | CVE-2021-31207 | One of the ProxyShell vulnerabilities |
Despite the lack of overlap, there are many well-known vulnerabilities at the top of both lists. Heartbleed and EternalBlue appear on the top 10 exploited list, while Hafnium, PrintNightmare, and ProxyShell make the top 10 most talked about CVEs.
The Log4j vulnerability is the only CVE that appears in both lists. This isn’t surprising considering the ubiquity of Log4j in modern software. It’s the second-most exploited vulnerability—far outpacing the CVEs directly below it. This, coupled with its appearance in the chatter list, puts it in a class of its own. In a brief period, it’s managed to outpace older CVEs that are arguably just as well known.
The CVE that recorded the most successful exploitations is a five-year-old vulnerability in PHPUnit. This is a popular unit-testing framework that’s used by many CMSes, such as Drupal, WordPress, MediaWiki, and Moodle.
Since many websites are built with these tools, this exploit can be a handy vector for gaining initial access to unpatched webservers. This also lines up with research we conducted last year, where this vulnerability was one of the most common Snort detections seen by Cisco Secure Firewall.
All four of the Microsoft Exchange Server vulnerabilities used in the Hafnium attacks appear in the most talked about list of CVEs. However, even when you add all four of these CVEs together, they still don’t come anywhere close to the counts seen in the top exploited CVEs.
If media attention is not a good predictor of use for exploitation, then what are the alternatives?
The Common Vulnerability Scoring System (CVSS) is a well-known framework for gauging the severity of vulnerabilities. We looked for CVEs from the KEV catalog that were ranked as “critical”—9.0 and above in the CVSSv3 specification. Examining the entire KEV catalog, 28% of the CVEs have a score of 9.0 or higher. Of the top 50 successfully exploited, 38% had such scores.
This is an improvement, but the CVSSv3 specification was released in 2015. Many CVEs in the KEV catalog predate this—19% of the entire catalog and 28% of the top 50—and have no score.
Using the previous CVSS specification does fill this gap—36% overall and 52% of the top 50 score 9.0 or higher. However, the older CVSS specification comes with its share of issues as well.
Another indicator worth exploring is remote control execution (RCE). A vulnerability with RCE grants an attacker the ability to access and control a vulnerable system from anywhere. It turns out that 45% of the CVEs in our dataset allow for RCE, and 66% of the top 50, making it the most worthwhile indicator analyzed.
Let’s summarize how we’ve honed our approach to determine if media attention and exploitation line up:
| Data set | Exploitation and Chatter lists | Number of CVEs |
| All CVEs | Appears in both top 50 | 2 |
| Appears in both top 50 (last 10 years) | 3 | |
| KEV Catalog | Appears in both top 50 | 6 |
| Appears in both top 10 | 1 |
And here’s a summary of our look at other indicators:
| KEV Catalog | Top 50 exploited | |
| CVSSv3 (9.0+) | 28% | 38% |
| CVSS (9.0+) | 36% | 52% |
| Allows for RCE | 45% | 66% |
All of this analysis provides a clear answer to our original question—the most regularly exploited CVEs aren’t the most talked about. Additional work highlights that monitoring variables like RCE can help with prioritization.
For illustrative purposes we’ve only looked at a few indicators that could be used to prioritize CVEs. While some did better than others, we don’t recommend relying on a single variable in making decisions about vulnerability management. Creating an approach that folds in multiple indicators is a far better strategy when it comes to real-world application of this data. And while our findings here speak to the larger picture, every network is different.
Regardless of which list they appear on, be it Successful Exploitations or Chatter Count, it’s important to point out that all these vulnerabilities are serious. Just because Hafnium has more talk than Heartbleed doesn’t make it any less dangerous if you have assets that are vulnerable to it. The fact is that while CVEs with more talk didn’t make the top of the exploitation list, they still managed to rack up tens of thousands of successful exploitations.
It’s important to know how to prioritize security updates, fixing those that expose you to the most risk as soon as possible. From our perspective, here are some basic elements in the Cisco Secure portfolio that can help.
Kenna Security, a pioneer in risk-based vulnerability management, relies on threat intel and prioritization to keep security and IT teams focused on risks. Using data science, Kenna processes and analyzes 18+ threat and exploit intelligence feeds, and 12.7+ billion managed vulnerabilities to give you an accurate view of your company’s risk. With our risk scoring and remediation intelligence, you get the info you need to make truly data-driven remediation decisions.
To responsibly protect a network, it’s important to monitor all assets that connect to it and ensure they’re kept up to date. Duo Device Trust can check the patch level of devices for you before they’re granted access to connect to corporate applications or sensitive data. You can even block access and enable self-remediation for devices that are found to be non-compliant.
How about remote workers? By leveraging the Network Visibility Module in Cisco Secure Client as a telemetry source, Cisco Secure Cloud Analytics can capture endpoint-specific user and device context to supply visibility into remote worker endpoint status. This can bolster an organization’s security posture by providing visibility on remote employees that are running software versions with vulnerabilities that need patching.
Lastly, for some “lateral thinking” about vulnerability management, take a look at this short video of one of our Advisory CISOs, Wolfgang Goerlich. Especially if you’re a fan of the music of the 1920s…
We’d love to hear what you think. Ask a Question, Comment Below, and Stay Connected with Cisco Secure on social!
Cisco Secure Social Channels
Authorities in the United States, Germany, the Netherlands and the U.K. last week said they dismantled the “RSOCKS” botnet, a collection of millions of hacked devices that were sold as “proxies” to cybercriminals looking for ways to route their malicious traffic through someone else’s computer. While the coordinated action did not name the Russian hackers allegedly behind RSOCKS, KrebsOnSecurity has identified its owner as a 35-year-old Russian man living abroad who also runs the world’s top spam forum.
The RUSdot mailer, the email spamming tool made and sold by the administrator of RSOCKS.
According to a statement by the U.S. Department of Justice, RSOCKS offered clients access to IP addresses assigned to devices that had been hacked:
“A cybercriminal who wanted to utilize the RSOCKS platform could use a web browser to navigate to a web-based ‘storefront’ (i.e., a public web site that allows users to purchase access to the botnet), which allowed the customer to pay to rent access to a pool of proxies for a specified daily, weekly, or monthly time period. The cost for access to a pool of RSOCKS proxies ranged from $30 per day for access to 2,000 proxies to $200 per day for access to 90,000 proxies.”
The DOJ’s statement doesn’t mention that RSOCKS has been in operation since 2014, when access to the web store for the botnet was first advertised on multiple Russian-language cybercrime forums.
The user “RSOCKS” on the Russian crime forum Verified changed his name to RSOCKS from a previous handle: “Stanx,” whose very first sales thread on Verified in 2016 quickly ran afoul of the forum’s rules and prompted a public chastisement by the forum’s administrator.
Verified was hacked twice in the past few years, and each time the private messages of all users on the forum were leaked. Those messages show that after being warned of his forum infraction, Stanx sent a private message to the Verified administrator detailing his cybercriminal bona fides.
“I am the owner of the RUSdot forum (former Spamdot),” Stanx wrote in Sept. 2016. “In spam topics, people know me as a reliable person.”
A Google-translated version of the Rusdot spam forum.
RUSdot is the successor forum to Spamdot, a far more secretive and restricted forum where most of the world’s top spammers, virus writers and cybercriminals collaborated for years before the community’s implosion in 2010. Even today, the RUSdot Mailer is advertised for sale at the top of the RUSdot community forum.
Stanx said he was a longtime member of several major forums, including the Russian hacker forum Antichat (since 2005), and the Russian crime forum Exploit (since April 2013). In an early post to Antichat in January 2005, Stanx disclosed that he is from Omsk, a large city in the Siberian region of Russia.
According to the cyber intelligence firm Intel 471, the user Stanx indeed registered on Exploit in 2013, using the email address stanx@rusdot.com, and the ICQ number 399611. A search in Google for that ICQ number turns up a cached version of a Vkontakte profile for a Denis “Neo” Kloster, from Omsk, Russia.
Cybersecurity firm Constella Intelligence shows that in 2017, someone using the email address istanx@gmail.com registered at the Russian freelancer job site fl.ru with the profile name of “Denis Kloster” and the Omsk phone number of 79136334444. Another record indexed by Constella suggests Denis’s real surname may in fact be “Emilyantsev” [Емельянцев].
That phone number is tied to the WHOIS registration records for multiple domain names over the years, including proxy[.]info, allproxy[.]info, kloster.pro and deniskloster.com.
A copy of the passport for Denis Kloster, as posted to his Vkontakte page in 2019. It shows that in Oct. 2019, he obtained a visa from the American Embassy in Bangkok, Thailand.
The “about me” section of DenisKloster.com says the 35-year-old was born in Omsk, that he got his first computer at age 12, and graduated from high school at 16. Kloster says he’s worked in many large companies in Omsk as a system administrator, web developer and photographer.
According to Kloster’s blog, his first real job was running an “online advertising” firm he founded called Internet Advertising Omsk (“riOmsk“), and that he even lived in New York City for a while.
“Something new was required and I decided to leave Omsk and try to live in the States,” Kloster wrote in 2013. “I opened an American visa for myself, it was not difficult to get. And so I moved to live in New York, the largest city in the world, in a country where all wishes come true. But even this was not enough for me, and since then I began to travel the world.”
The current version of the About Me page on Kloster’s site says he closed his advertising business in 2013 to travel the world and focus on his new company: One that provides security and anonymity services to customers around the world. Kloster’s vanity website and LinkedIn page both list him as CEO of a company called “SL MobPartners.”
In 2016, Deniskloster.com featured a post celebrating three years in operation. The anniversary post said Kloster’s anonymity business had grown to nearly two dozen employees, most of whom were included in a group photo posted to that article (and some of whom Kloster thanked by their first names and last initials).
The employees who kept things running for RSOCKS, circa 2016.
“Thanks to you, we are now developing in the field of information security and anonymity!,” the post enthuses. “We make products that are used by thousands of people around the world, and this is very cool! And this is just the beginning!!! We don’t just work together and we’re not just friends, we’re Family.”
Mr. Kloster did not respond to repeated requests for comment.
It’s not clear if the coordinated takedown targeting the RSOCKS botnet will be permanent, as the botnet’s owners could simply rebuild — and possibly rebrand — their crime machine. Based on the RSOCKS owner’s posts, that is exactly what they intend to do.
“RSocks ceases to exist,” wrote the Rsocks account on the BlackHatWorld forum on June 17. “But don’t worry. All the active plans and fund balances will be transferred to another service. Stay tuned. We will inform you about its name and all the details later.”
Rsocks told the BlackHatWorld community they would be back soon under a new name.
Malware-based proxy services like RSOCKS have struggled to remain competitive in a cybercrime market with increasingly sophisticated proxy services that offer many additional features. The demise of RSOCKS follows closely on the heels of VIP72[.]com, a competing proxy botnet service that operated for a decade before its owners pulled the plug on the service last year.
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