Category: Proofpoint

Thread hijacking attacks. They happen when someone you know has their email account compromised, and you are suddenly dropped into an existing conversation between the sender and someone else. These missives draw on the recipient’s natural curiosity about being copied on a private discussion, which is modified to include a malicious link or attachment. Here’s the story of a recent thread hijacking attack in which a journalist was copied on a phishing email from the unwilling subject of a recent scoop.

In Sept. 2023, the Pennsylvania news outlet LancasterOnline.com published a story about Adam Kidan, a wealthy businessman with a criminal past who is a major donor to Republican causes and candidates, including Rep. Lloyd Smucker (R-Pa).

The LancasterOnline story about Adam Kidan.

Several months after that piece ran, the story’s author Brett Sholtis received two emails from Kidan, both of which contained attachments. One of the messages appeared to be a lengthy conversation between Kidan and a colleague, with the subject line, “Re: Successfully sent data.” The second missive was a more brief email from Kidan with the subject, “Acknowledge New Work Order,” and a message that read simply, “Please find the attached.”

Sholtis said he clicked the attachment in one of the messages, which then launched a web page that looked exactly like a Microsoft Office 365 login page. An analysis of the webpage reveals it would check any submitted credentials at the real Microsoft website, and return an error if the user entered bogus account information. A successful login would record the submitted credentials and forward the victim to the real Microsoft website.

But Sholtis said he didn’t enter his Outlook username and password. Instead, he forwarded the messages to LancasterOneline’s IT team, which quickly flagged them as phishing attempts.

LancasterOnline’s Executive Editor Tom Murse said the two phishing messages from Mr. Kidan raised eyebrows in the newsroom because Kidan had threatened to sue the news outlet multiple times over Sholtis’s story.

“We were just perplexed,” Murse said. “It seemed to be a phishing attempt but we were confused why it would come from a prominent businessman we’ve written about. Our initial response was confusion, but we didn’t know what else to do with it other than to send it to the FBI.”

The phishing lure attached to the thread hijacking email from Mr. Kidan.

In 2006, Kidan was sentenced to 70 months in federal prison after pleading guilty to defrauding lenders along with Jack Abramoff, the disgraced lobbyist whose corruption became a symbol of the excesses of Washington influence peddling. He was paroled in 2009, and in 2014 moved his family to a home in Lancaster County, Pa.

The FBI hasn’t responded to LancasterOnline’s tip. Messages sent by KrebsOnSecurity to Kidan’s emails addresses were returned as blocked. Messages left with Mr. Kidan’s company, Empire Workforce Solutions, went unreturned.

No doubt the FBI saw the messages from Kidan for what they likely were: The result of Mr. Kidan having his Microsoft Outlook account compromised and used to send malicious email to people in his contacts list.

Thread hijacking attacks are hardly new, but that is mainly true because many Internet users still don’t know how to identify them. The email security firm Proofpoint says it has tracked north of 90 million malicious messages in the last five years that leverage this attack method.

One key reason thread hijacking is so successful is that these attacks generally do not include the tell that exposes most phishing scams: A fabricated sense of urgency. A majority of phishing threats warn of negative consequences should you fail to act quickly — such as an account suspension or an unauthorized high-dollar charge going through.

In contrast, thread hijacking campaigns tend to patiently prey on the natural curiosity of the recipient.

Ryan Kalember, chief strategy officer at Proofpoint, said probably the most ubiquitous examples of thread hijacking are “CEO fraud” or “business email compromise” scams, wherein employees are tricked by an email from a senior executive into wiring millions of dollars to fraudsters overseas.

But Kalember said these low-tech attacks can nevertheless be quite effective because they tend to catch people off-guard.

“It works because you feel like you’re suddenly included in an important conversation,” Kalember said. “It just registers a lot differently when people start reading, because you think you’re observing a private conversation between two different people.”

Some thread hijacking attacks actually involve multiple threat actors who are actively conversing while copying — but not addressing — the recipient.

“We call these mutli-persona phishing scams, and they’re often paired with thread hijacking,” Kalember said. “It’s basically a way to build a little more affinity than just copying people on an email. And the longer the conversation goes on, the higher their success rate seems to be because some people start replying to the thread [and participating] psycho-socially.”

The best advice to sidestep phishing scams is to avoid clicking on links or attachments that arrive unbidden in emails, text messages and other mediums. If you’re unsure whether the message is legitimate, take a deep breath and visit the site or service in question manually — ideally, using a browser bookmark so as to avoid potential typosquatting sites.

Conti — one of the most ruthless and successful Russian ransomware groups — publicly declared during the height of the COVID-19 pandemic that it would refrain from targeting healthcare providers. But new information confirms this pledge was always a lie, and that Conti has launched more than 200 attacks against hospitals and other healthcare facilities since first surfacing in 2018 under its earlier name, “Ryuk.”

On April 13, Microsoft said it executed a legal sneak attack against Zloader, a remote access trojan and malware platform that multiple ransomware groups have used to deploy their malware inside victim networks. More specifically, Microsoft obtained a court order that allowed it to seize 65 domain names that were used to maintain the Zloader botnet.

Microsoft’s civil lawsuit against Zloader names seven “John Does,” essentially seeking information to identify cybercriminals who used Zloader to conduct ransomware attacks. As the company’s complaint notes, some of these John Does were associated with lesser ransomware collectives such as Egregor and Netfilim.

But according to Microsoft and an advisory from the U.S. Cybersecurity & Infrastructure Security Agency (CISA), Zloader had a special relationship with Ryuk/Conti, acting as a preferred distribution platform for deploying Ryuk/Conti ransomware.

Several parties backed Microsoft in its legal efforts against Zloader by filing supporting declarations, including Errol Weiss, a former penetration tester for the U.S. National Security Agency (NSA). Weiss now serves as the chief security officer of the Health Information Sharing & Analysis Center (H-ISAC), an industry group that shares information about cyberattacks against healthcare providers.

Weiss said ransomware attacks from Ryuk/Conti have impacted hundreds of healthcare facilities across the United States, including facilities located in 192 cities and 41 states and the District of Columbia.

“The attacks resulted in the temporary or permanent loss of IT systems that support many of the provider delivery functions in modern hospitals resulting in cancelled surgeries and delayed medical care,” Weiss said in a declaration (PDF) with the U.S. District Court for the Northern District of Georgia.

“Hospitals reported revenue losses due to Ryuk infections of nearly $100 million from data I obtained through interviews with hospital staff, public statements, and media articles,” Weiss wrote. “The Ryuk attacks also caused an estimated $500 million in costs to respond to the attacks – costs that include ransomware payments, digital forensic services, security improvements and upgrading impacted systems plus other expenses.”

The figures cited by Weiss appear highly conservative. A single attack by Ryuk/Conti in May 2021 against Ireland’s Health Service Executive, which operates the country’s public health system, resulted in massive disruptions to healthcare in Ireland. In June 2021, the HSE’s director general said the recovery costs for that attack were likely to exceed USD $600 million.

Conti ravaged the healthcare sector throughout 2020, and leaked internal chats from the Conti ransomware group show the gang had access to more than 400 healthcare facilities in the U.S. alone by October 2020.

On Oct. 28, 2020, KrebsOnSecurity broke the news that FBI and DHS officials had seen reliable intelligence indicating the group planned to ransom many of these care facilities simultaneously. Hours after that October 2020 piece ran, I heard from a respected H-ISAC security professional who questioned whether it was worth getting the public so riled up. The story had been updated multiple times throughout the day, and there were at least five healthcare organizations hit with ransomware within the span of 24 hours.

“I guess it would help if I understood what the baseline is, like how many healthcare organizations get hit with ransomware on average in one week?” I asked the source.

“It’s more like one a day,” the source confided.

A report in February 2022 from Sophos found Conti orchestrated a cyberattack against a Canadian healthcare provider in late 2021. Security software firm Emsisoft found that at least 68 healthcare providers suffered ransomware attacks last year.

While Conti is just one of many ransomware groups threatening the healthcare industry, it seems likely that ransomware attacks on the healthcare sector are underreported. Perhaps this is because a large percentage of victims are paying a ransom demand to keep their data (and news of their breach) confidential. A survey published in February by email security provider Proofpoint found almost 60 percent of victims hit by ransomware paid their extortionists.

Or perhaps it’s because many crime groups have shifted focus away from deploying ransomware and toward stealing data and demanding payment not to publish the information. Conti shames victims who refuse to pay a ransom by posting their internal data on their darkweb blog.

Since the beginning of 2022, Conti has claimed responsibility for hacking a cancer testing lab, a medical prescription service online, a biomedical testing facility, a pharmaceutical company, and a spinal surgery center.

The Healthcare Information and Management Systems Society recently released its 2021 HIMSS Healthcare Cybersecurity Survey (PDF), which interviewed 167 healthcare cybersecurity professionals and found 67 percent had experienced a “significant security incident” in the past year.

The survey also found that just six percent or less of respondent’s information technology budgets were devoted to cybersecurity, although roughly 60 percent of respondents said their cybersecurity budgets would increase in 2022. Last year, just 79 percent of respondents said they’d fully implemented antivirus or other anti-malware systems; only 43 percent reported they’d fully implemented intrusion detection and prevention technologies.

The FBI says Conti typically gains access to victim networks through weaponized malicious email links, attachments, or stolen Remote Desktop Protocol (RDP) credentials, and that it weaponizes Microsoft Office documents with embedded Powershell scripts — initially staging Cobalt Strike via the Office documents and then dropping Emotet onto the network — giving them the ability to deploy ransomware. The FBI said Conti has been observed inside victim networks between four days and three weeks on average before deploying Conti ransomware.