Teach a Man to Phish and He’s Set for Life

One frustrating aspect of email phishing is the frequency with which scammers fall back on tried-and-true methods that really have no business working these days. Like attaching a phishing email to a traditional, clean email message, or leveraging link redirects on LinkedIn, or abusing an encoding method that makes it easy to disguise booby-trapped Microsoft Windows files as relatively harmless documents.

KrebsOnSecurity recently heard from a reader who was puzzled over an email he’d just received saying he needed to review and complete a supplied W-9 tax form. The missive was made to appear as if it were part of a mailbox delivery report from Microsoft 365 about messages that had failed to deliver.

The reader, who asked to remain anonymous, said the phishing message contained an attachment that appeared to have a file extension of “.pdf,” but something about it seemed off. For example, when he downloaded and tried to rename the file, the right arrow key on the keyboard moved his cursor to the left, and vice versa.

The file included in this phishing scam uses what’s known as a “right-to-left override” or RLO character. RLO is a special character within unicode — an encoding system that allows computers to exchange information regardless of the language used — that supports languages written from right to left, such as Arabic and Hebrew.

Look carefully at the screenshot below and you’ll notice that while Microsoft Windows says the file attached to the phishing message is named “lme.pdf,” the full filename is “fdp.eml” spelled backwards. In essence, this is a .eml file — an electronic mail format or email saved in plain text — masquerading as a .PDF file.

“The email came through Microsoft Office 365 with all the detections turned on and was not caught,” the reader continued. “When the same email is sent through Mimecast, Mimecast is smart enough to detect the encoding and it renames the attachment to ‘___fdp.eml.’ One would think Microsoft would have had plenty of time by now to address this.”

Indeed, KrebsOnSecurity first covered RLO-based phishing attacks back in 2011, and even then it wasn’t a new trick.

Opening the .eml file generates a rendering of a webpage that mimics an alert from Microsoft about wayward messages awaiting restoration to your inbox. Clicking on the “Restore Messages” link there bounces you through an open redirect on LinkedIn before forwarding to the phishing webpage.

As noted here last year, scammers have long taken advantage of a marketing feature on the business networking site which lets them create a LinkedIn.com link that bounces your browser to other websites, such as phishing pages that mimic top online brands (but chiefly Linkedin’s parent firm Microsoft).

The landing page after the LinkedIn redirect displays what appears to be an Office 365 login page, which is naturally a phishing website made to look like an official Microsoft Office property.

In summary, this phishing scam uses an old RLO trick to fool Microsoft Windows into thinking the attached file is something else, and when clicked the link uses an open redirect on a Microsoft-owned website (LinkedIn) to send people to a phishing page that spoofs Microsoft and tries to steal customer email credentials.

According to the latest figures from Check Point Software, Microsoft was by far the most impersonated brand for phishing scams in the second quarter of 2023, accounting for nearly 30 percent of all brand phishing attempts.

An unsolicited message that arrives with one of these .eml files as an attachment is more than likely to be a phishing lure. The best advice to sidestep phishing scams is to avoid clicking on links that arrive unbidden in emails, text messages and other mediums. Most phishing scams invoke a temporal element that warns of dire consequences should you fail to respond or act quickly.

If you’re unsure whether a message is legitimate, take a deep breath and visit the site or service in question manually — ideally, using a browser bookmark to avoid potential typosquatting sites.

CISA Order Highlights Persistent Risk at Network Edge

The U.S. government agency in charge of improving the nation’s cybersecurity posture is ordering all federal agencies to take new measures to restrict access to Internet-exposed networking equipment. The directive comes amid a surge in attacks targeting previously unknown vulnerabilities in widely used security and networking appliances.

Under a new order from the Cybersecurity and Infrastructure Security Agency (CISA), federal agencies will have 14 days to respond to any reports from CISA about misconfigured or Internet-exposed networking equipment. The directive applies to any networking devices — such as firewalls, routers and load balancers — that allow remote authentication or administration.

The order requires federal departments to limit access so that only authorized users on an agency’s local or internal network can reach the management interfaces of these devices. CISA’s mandate follows a slew of recent incidents wherein attackers exploited zero-day flaws in popular networking products to conduct ransomware and cyber espionage attacks on victim organizations.

Earlier today, incident response firm Mandiant revealed that since at least October 2022, Chinese cyber spies have been exploiting a zero-day vulnerability in many email security gateway (ESG) appliances sold by California-based Barracuda Networks to hoover up email from organizations using these devices.

Barracuda was alerted to the exploitation of a zero-day in its products in mid-May, and two days later the company pushed a security update to address the flaw in all affected devices. But last week, Barracuda took the highly unusual step of offering to replace compromised ESGs, evidently in response to malware that altered the systems in such a fundamental way that they could no longer be secured remotely with software updates.

According to Mandiant, a previously unidentified Chinese hacking group was responsible for exploiting the Barracuda flaw, and appeared to be searching through victim organization email records for accounts “belonging to individuals working for a government with political or strategic interest to [China] while this victim government was participating in high-level, diplomatic meetings with other countries.”

When security experts began raising the alarm about a possible zero-day in Barracuda’s products, the Chinese hacking group altered their tactics, techniques and procedures (TTPs) in response to Barracuda’s efforts to contain and remediate the incident, Mandiant found.

Mandiant said the attackers will continue to change their tactics and malware, “especially as network defenders continue to take action against this adversary and their activity is further exposed by the infosec community.”

Meanwhile, this week we learned more details about the ongoing exploitation of a zero-day flaw in a broad range of virtual private networking (VPN) products made by Fortinet — devices many organizations rely on to facilitate remote network access for employees.

On June 11, Fortinet released a half-dozen security updates for its FortiOS firmware, including a weakness that researchers said allows an attacker to run malware on virtually any Fortinet SSL VPN appliance. The researchers found that just being able to reach the management interface for a vulnerable Fortinet SSL VPN appliance was enough to completely compromise the devices.

“This is reachable pre-authentication, on every SSL VPN appliance,” French vulnerability researcher Charles Fol tweeted. “Patch your #Fortigate.”

In details published on June 12, Fortinet confirmed that one of the vulnerabilities (CVE-2023-27997) is being actively exploited. The company said it discovered the weakness in an internal code audit that began in January 2023 — when it learned that Chinese hackers were exploiting a different zero-day flaw in its products.

Shodan.io, the search engine made for finding Internet of Things devices, reports that there are currently more than a half-million vulnerable Fortinet devices reachable via the public Internet.

The new cybersecurity directive from CISA orders agencies to remove any networking device management interfaces from the internet by making them only accessible from an internal enterprise network (CISA recommends an isolated management network). CISA also says agencies should “deploy capabilities, as part of a Zero Trust Architecture, that enforce access control to the interface through a policy enforcement point separate from the interface itself (preferred action).”

Security experts say CISA’s directive highlights the reality that cyberspies and ransomware gangs are making it increasingly risky for organizations to expose any devices to the public Internet, because these groups have strong incentives to probe such devices for previously unknown security vulnerabilities.

The most glaring example of this dynamic can be seen in the frequency with which ransomware groups have discovered and pounced on zero-day flaws in widely-used file transfer applications. One ransomware gang in particular — Cl0p — has repeatedly exploited zero day bugs in various file transfer appliances to extort tens of millions of dollars from hundreds of ransomware victims.

On February 2, KrebsOnSecurity broke the news that attackers were exploiting a zero-day vulnerability in the GoAnywhere file transfer appliance by Fortra. By the time security updates were available to fix the vulnerability, Cl0p had already used it to steal data from more than a hundred organizations running Fortra’s appliance.

According to CISA, on May 27, Cl0p began exploiting a previously unknown flaw in MOVEit Transfer, a popular Internet-facing file transfer application. MOVEit parent Progress Software has since released security updates to address the weakness, but Cl0p claims to have already used it to compromise hundreds of victim organizations. TechCrunch has been tracking the fallout from victim organizations, which range from banks and insurance providers to universities and healthcare entities.

The always on-point weekly security news podcast Risky Business has recently been urging organizations to jettison any and all FTP appliances, noting that Cl0p (or another crime gang) is likely to visit the same treatment on other FTP appliance vendors.

But that sound advice doesn’t exactly scale for mid-tier networking devices like Barracuda ESGs or Fortinet SSL VPNs, which are particularly prominent in small to mid-sized organizations.

“It’s not like FTP services, you can’t tell an enterprise [to] turn off the VPN [because] the productivity hit of disconnecting the VPN is terminal, it’s a non-starter,” Risky Business co-host Adam Boileau said on this week’s show. “So how to mitigate the impact of having to use a domain-joined network appliance at the edge of your network that is going to get zero-day in it? There’s no good answer.”

Risky Business founder Patrick Gray said the COVID-19 pandemic breathed new life into entire classes of networking appliances that rely on code which was never designed with today’s threat models in mind.

“In the years leading up to the pandemic, the push towards identity-aware proxies and zero trust everything and moving away from this type of equipment was gradual, but it was happening,” Gray said. “And then COVID-19 hit and everybody had to go work from home, and there really was one option to get going quickly — which was to deploy VPN concentrators with enterprise features.”

Gray said the security industry had been focused on building the next generation of remote access tools that are more security-hardened, but when the pandemic hit organizations scrambled to cobble together whatever they could.

“The only stuff available in the market was all this old crap that is not QA’d properly, and every time you shake them CVEs fall out,” Gray remarked, calling the pandemic, “a shot in the arm” to companies like Fortinet and Barracuda.

“They sold so many VPNs through the pandemic and this is the hangover,” Gray said. “COVID-19 extended the life of these companies and technologies, and that’s unfortunate.”