The incoming phone call flashes on a victim’s phone. It may only last a few seconds, but can end with the victim handing over codes that give cybercriminals the ability to hijack their online accounts or drain their crypto and digital wallets.

“This is the PayPal security team here. We’ve detected some unusual activity on your account and are calling you as a precautionary measure,” the caller’s robotic voice says. “Please enter the six-digit security code that we’ve sent to your mobile device.”

The victim, ignorant of the caller’s malicious intentions, taps into their phone keypad the six-digit code they just received by text message.

“Got that boomer!” a message reads on the attacker’s console.

In some cases, the attacker might also send a phishing email with the aim of capturing the victim’s password. But oftentimes, that code from their phone is all the attacker needs to break into a victim’s online account. By the time the victim ends the call, the attacker has already used the code to log in to the victim’s account as if they were the rightful owner.

Since mid-2023, an interception operation called Estate has enabled hundreds of members to carry out thousands of automated phone calls to trick victims into entering one-time passcodes, TechCrunch has learned. Estate helps attackers defeat security features like multi-factor authentication, which rely on a one-time passcode either sent to a person’s phone or email or generated from their device using an authenticator app. Stolen one-time passcodes can grant attackers access to a victim’s bank accounts, credit cards, crypto and digital wallets and online services. Most of the victims have been in the United States.

But a bug in Estate’s code exposed the site’s back-end database, which was not encrypted. Estate’s database contains details of the site’s founder and its members, and line-by-line logs of each attack since the site launched, including the phone numbers of victims that were targeted, when and by which member. 

Vangelis Stykas, a security researcher and chief technology officer at Atropos.ai, provided the Estate database to TechCrunch for analysis.

The back-end database provides a rare insight into how a one-time passcode interception operation works. Services like Estate advertise their offerings under the guise of providing an ostensibly legitimate service for allowing security practitioners to stress-test resilience to social engineering attacks, but fall in a legal gray space because they allow their members to use these services for malicious cyberattacks. In the past, authorities have prosecuted operators of similar sites dedicated to automating cyberattacks for supplying their services to criminals. 

The database contains logs for more than 93,000 attacks since Estate launched last year, targeting victims who have accounts with Amazon, Bank of America, Capital One, Chase, Coinbase, Instagram, Mastercard, PayPal, Venmo, Yahoo (which owns TechCrunch) and many others.

Some of the attacks also show efforts to hijack phone numbers by carrying out SIM swap attacks — one campaign was simply titled “ur getting sim swapped buddy” — and threatening to dox victims.

The founder of Estate, a Danish programmer in their early 20s, told TechCrunch in an email last week, “I do not operate the site anymore.” The founder, despite efforts to conceal Estate’s online operations, misconfigured Estate’s server that exposed its real-world location in a data center in the Netherlands.

Estate advertises itself as able to “create tailored OTP solutions that match your needs perfectly,” and explains that “our custom scripting option puts you in control.” Estate members tap into the global phone network by posing as legitimate users to gain access to upstream communications providers. One provider was Telnyx, whose chief executive David Casem told TechCrunch that the company blocked Estate’s accounts and that an investigation was underway.

Although Estate is careful not to outwardly use explicit language that could incite or encourage malicious cyberattacks, the database shows that Estate is used almost exclusively for criminality. 

“These kinds of services form the backbone of the criminal economy,” said Allison Nixon, chief research officer at Unit 221B, a cybersecurity firm known for investigating cybercrime groups. “They make slow tasks efficient. This means more people receive scams and threats in general. More old people lose their retirement due to crime — compared to the days before these types of services existed.”

How Estate operates

Estate tried to keep a low profile by hiding its website from search engines and bringing on new members by word of mouth. According to its website, new members can sign in to Estate only with a referral code from an existing member, which keeps the number of users low to avoid detection by the upstream communications providers that Estate relies on.

Once through the door, Estate provides members with tools for searching for previously breached account passwords of their would-be victims, leaving one-time codes as the only obstacle to hijack the targets’ accounts. Estate’s tools also allow members to use custom-made scripts containing instructions for tricking targets into turning over their one-time passcodes. 

Some attack scripts are designed instead to validate stolen credit card numbers by tricking the victim into turning over the security code on the back of their payment card.

According to the database, one of the biggest calling campaigns on Estate targeted older victims under the assumption that “boomers” are more likely to take an unsolicited phone call than younger generations. The campaign, which accounted for about a thousand phone calls, relied on a script that kept the cybercriminal apprised of each attempted attack.

“The old f— answered!” would flash in the console when their victim picked up the call, and “Life support unplugged” would show when the attack succeeded.

The database shows that Estate’s founder is aware that their clientele are largely criminal actors, and Estate has long promised privacy for its members.

“We do not log any data, and we do not require any personal information to use our services,” reads Estate’s website, a snub to the identity checks that upstream telecom providers and tech companies typically require before letting customers onto their networks.

But that isn’t strictly true. Estate logged every attack its members carried out in granular detail dating back to the site’s launch in mid-2023. And the site’s founder retained access to server logs that provided a real-time window into what was happening on Estate’s server at any given time, including every call made by its members, as well as any time a member loaded a page on Estate’s website.

The database shows that Estate also keeps track of email addresses of prospective members. One of those users said they wanted to join Estate because they recently “started buying ccs” — referring to credit cards — and believed Estate was more trustworthy than buying a bot from an unknown seller. The user was later approved to become an Estate member, the records show.

The exposed database shows that some members trusted Estate’s promise of anonymity by leaving fragments of their own identifiable information — including email addresses and online handles — in the scripts they wrote and attacks they carried out.

Estate’s database also contains its members’ attack scripts, which reveal the specific ways that attackers exploit weaknesses in how tech giants and banks implement security features, like one-time passcodes, for verifying customer identities. TechCrunch is not describing the scripts in detail, as doing so could aid cybercriminals in carrying out attacks.

Veteran security reporter Brian Krebs, who previously reported on a one-time passcode operation in 2021, said these kinds of criminal operations make clear why you should “never provide any information in response to an unsolicited phone call.”

“It doesn’t matter who claims to be calling: If you didn’t initiate the contact, hang up,” Krebs wrote. That advice still holds true today.

But while services that offer using one-time passcodes still provide better security to users than services that don’t, the ability for cybercriminals to circumvent these defenses shows that tech companies, banks, crypto wallets and exchanges, and telecom companies have more work to do. 

Unit 221B’s Nixon said companies are in a “forever battle” with bad actors looking to abuse their networks, and that authorities should step up efforts to crack down on these services.

“The missing piece is we need law enforcement to arrest crime actors that make themselves such a nuisance,” said Nixon. “Young people are deliberately making a career out of this, because they convince themselves they’re ‘just a platform’ and ‘not responsible for crime’ facilitated by their project.”

“They hope to make easy money in the scam economy. There are influencers that encourage unethical ways to make money online. Law enforcement needs to stop this.”

Read more on TechCrunch:

• Threat actor scraped 49M Dell customer addresses
• Encrypted services Apple, Proton and Wire helped Spanish police identify activist
• UHG CEO says ‘maybe a third’ of US citizens affected by recent hack
• What we learned from the indictment of LockBit’s mastermind

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