news.sophos.com
Written by Ross McKerchar
September 22, 2025
A Sophos employee was phished, but we countered the threat with an end-to-end defense process
If you work in cybersecurity, you’ve probably heard the time-honored adage about cyber attacks: “It’s not a matter of if, but when.” Perhaps a better way to think of it is this: while training, experience, and familiarity with social engineering techniques help, anyone can fall for a well-constructed ruse. Everyone – including security researchers – has a vulnerability that could make them susceptible, given the right situation, timing, and circumstances.
Cybersecurity companies aren’t immune by any means. In March 2025, a senior Sophos employee fell victim to a phishing email and entered their credentials into a fake login page, leading to a multi-factor authentication (MFA) bypass and a threat actor trying – and failing – to worm their way into our network.
We’ve published an external root cause analysis (RCA) about this incident on our Trust Center, which dives into the details – but the incident raised some interesting broader topics that we wanted to share some thoughts on.
First, it’s important to note that MFA bypasses are increasingly common. As MFA has become more widespread, threat actors have adapted, and several phishing frameworks and services now incorporate MFA bypass capabilities (another argument for the wider adoption of passkeys).
Second, we’re sharing the details of this incident not to highlight that we successfully repelled an attack – that’s our day job – but because it’s a good illustration of an end-to-end defense process, and has some interesting learning points.
Third, three things were key to our response: controls, cooperation, and culture.
Controls
Our security controls are layered, with the objective of being resilient to human failure and bypasses of earlier layers. The guiding principle behind a ‘defense-in-depth’ security policy is that when one control is bypassed, or fails, others should kick in – providing protection across as much of the cyber kill chain as possible.
As we discussed in the corresponding RCA, this incident involved multiple layers – email security, MFA, a Conditional Access Policy (CAP), device management, and account restrictions. While the threat actor bypassed some of those layers, subsequent controls were then triggered.
Crucially, however, we didn’t sit on our laurels after the incident. The threat actor was unsuccessful, but we didn’t congratulate ourselves and get on with our day. We investigated every aspect of the attack, conducted an internal root cause analysis, and assessed the performance of every control involved. Where a control was bypassed, we reviewed why this was the case and what we could do to improve it. Where a control worked effectively, we asked ourselves what threat actors might do in the future to bypass it, and then investigated how to mitigate against that.
Cooperation
Our internal teams work closely together all the time, and one of the key outcomes of that is a cooperative culture – particularly when there’s an urgent and active threat, whether internal or affecting our customers.
Sophos Labs, Managed Detection and Response (MDR), Internal Detection and Response (IDR), and our internal IT team worked within their different specialties and areas of expertise to eliminate the threat, sharing information and insights. Going forward, we’re looking at ways to improve our intelligence-gathering capabilities and tightening feedback loops – not just internally, but within the wider security community. Ingesting and operationalizing intelligence, making it actionable, and proactively using it to defend our estate, is a key priority. While we responded effectively to this incident, we can always be better.
Culture
We try to foster a culture in which the predominant focus is solving the problem and making things safe, rather than apportioning blame or criticizing colleagues for mistakes – and we don’t reprimand or discipline users who click on phishing links.
The employee in this incident felt able to directly inform colleagues that they had fallen for a phishing lure. In some organizations, users may not feel comfortable admitting to a mistake, whether that’s due to fear of reprisal or personal embarrassment. Others may hope that if they ignore a suspicious incident, the problem will go away. At Sophos, all users – whatever their role and level of seniority – are encouraged to report any suspicions. As we noted at the beginning of this article, we know that anyone can fall for a social engineering ruse given the right circumstances.
It’s often said – not necessarily helpfully – that humans are the weakest link in security. But they are also often the first line of defense, and can play a vital part in notifying security teams, validating automated alerts (or even alerting security themselves if technical controls fail), and providing additional context and intelligence.
Conclusion
An attacker breached our perimeter, but a combination of controls, cooperation, and culture meant that they were severely restricted in what they could do, before we removed them from our systems. Our post-incident review, and the lessons we took from it, means that our security posture is stronger, in readiness for the next attempt. By publicly and transparently sharing those lessons both here and in the RCA, we hope yours will be too.
Ransomware actor exploited RMM to access multiple organizations; Sophos EDR blocked encryption on customer’s network
Sophos MDR recently responded to a targeted attack involving a Managed Service Provider (MSP). In this incident, a threat actor gained access to the MSP’s remote monitoring and management (RMM) tool, SimpleHelp, and then used it to deploy DragonForce ransomware across multiple endpoints. The attackers also exfiltrated sensitive data, leveraging a double extortion tactic to pressure victims into paying the ransom.
Sophos MDR has medium confidence the threat actor exploited a chain of vulnerabilities that were released in January 2025:
CVE-2024-57727: Multiple path traversal vulnerabilities
CVE-2024-57728: Arbitrary file upload vulnerability
CVE-2024-57726: Privilege escalation vulnerability
DragonForce
DragonForce ransomware is an advanced and competitive ransomware-as-a-service (RaaS) brand that first emerged in mid-2023. As discussed in recent research from Sophos Counter Threat Unit (CTU), DragonForce began efforts in March to rebrand itself as a “cartel” and shift to a distributed affiliate branding model.
Coinciding with this effort to appeal to a wider range of affiliates, DragonForce recently garnered attention in the threat landscape for claiming to “take over” the infrastructure of RansomHub. Reports also suggest that well-known ransomware affiliates, including Scattered Spider (UNC3944) who was formerly a RansomHub affiliate, have been using DragonForce in attacks targeting multiple large retail chains in the UK and the US.
The incident
Sophos MDR was alerted to the incident by detection of a suspicious installation of a SimpleHelp installer file. The installer was pushed via a legitimate SimpleHelp RMM instance, hosted and operated by the MSP for their clients. The attacker also used their access through the MSP’s RMM instance to gather information on multiple customer estates managed by the MSP, including collecting device names and configuration, users, and network connections.
One client of the MSP was enrolled with Sophos MDR and had Sophos XDR endpoint protection deployed. Through a combination of behavioral and malware detection and blocking by Sophos endpoint protection and MDR actions to shut down attacker access to the network, thwarting the ransomware and double extortion attempt on that customer’s network. However, the MSP and clients that were not using Sophos MDR were impacted by both the ransomware and data exfiltration. The MSP engaged Sophos Rapid Response to provide digital forensics and incident response on their environment.
The dawn of our fifth year deepens our understanding of the enemies at the gate, and some tensions inside it; plus, an anniversary gift from us to you
The Gootloader malware family uses a distinctive form of social engineering to infect computers: Its creators lure people to visit compromised, legitimate WordPress websites using hijacked Google search results, present the visitors to these sites with a simulated online message board, and link to the malware from a simulated “conversation” where a fake visitor asks a fake site admin the exact question that the victim was searching for an answer to.
Open-source intelligence reveals the server-side code of this pernicious SEO-driven malware – without needing a lawyer afterward
A sudden disruption of a major phishing-as-a-service provider leads to the rise of another…that looks very familiar
Last month, Sophos X-Ops reported several MDR cases where threat actors exploited a vulnerability in Veeam backup servers. We continue to track the activities of this threat cluster, which recently…
The Internet is full of cats—and in this case, malware-delivering fake cat websites used for very targeted search engine optimization.
Sophos X-Ops unveils five-year investigation tracking China-based groups targeting perimeter devices
Familiar ransomware develops an appetite for passwords to third-party sites
Sophos discovers the threat actors behind RansomHub ransomware using EDRKillShifter in attacks
The “Mad Liberator” ransomware group leverages social-engineering moves to watch out for
Sophos Managed Detection and Response initiated a threat hunt across all customers after the detection of abuse of a vulnerable legitimate VMware executable (vmnat.exe) to perform dynamic link library (DLL) side-loading on one customer’s network. In a search for similar incidents in telemetry, MDR ultimately uncovered a complex, persistent cyberespionage campaign targeting a high-profile government organization in Southeast Asia. As described in the first part of this report, we identified at least three distinct clusters of intrusion activity present in the organization’s network from at least March 2023 through December 2023.
The three security threat activity clusters—which we designated as Alpha (STAC1248), Bravo (STAC1870), and Charlie (STAC1305) – are assessed with high confidence to operate on behalf of Chinese state interests. In this continuation of our report, we will provide deeper technical analysis of the three activity clusters, including the tactics, techniques, and procedures (TTPs) used in the campaign, aligned to activity clusters where possible. We also provide additional technical details on prior compromises within the same organization that appear to be connected to the campaign.
Cheap ransomware is being sold for one-time use on dark web forums, allowing inexperienced freelancers to get into cybercrime without any interaction with affiliates.
Researchers at the intelligence unit at the cybersecurity firm Sophos found 19 ransomware varieties being offered for sale or advertised as under development on four forums from June 2023 to February 2024.
First released in May 2023, an EDR killer – and the vulnerable Zemana drivers it leverages – are still of interest to threat actors, along with variants and ported versions
UK-based cybersecurity firm Sophos this week announced patches for an exploited vulnerability in Firewall versions that have reached End-of-Life (EOL).
The critical-severity flaw, tracked as CVE-2022-3236, was found to impact versions 19.0 MR1 (19.0.1) and older of the product. It was originally patched in September 2022, but only in supported versions of Sophos Firewall.
Sophos describes the security defect as a code injection issue in the Firewall’s User Portal and Webadmin components, allowing attackers to achieve remote code execution (RCE).
Sophos was forced to backport a security update for CVE-2022-3236 for end-of-life (EOL) firewall firmware versions after discovering hackers actively exploiting the flaw in attacks.
A social engineering phone call lends authenticity to the attacker’s malicious email
Imagine if you clicked on a harmless-looking image, but an unknown application fired up instead…
