What are the most common cybersecurity threats faced by accounting firms?

Threats such as phishing, ransomware, insider threats, and unsecured remote work environments continue to evolve, making robust cybersecurity measures essential. This article highlights the most pressing cybersecurity risks in 2025 we ourselves are facing, and provides actionable recommendations to mitigate them. From implementing multi-factor authentication and employee training to securing third-party integrations and defending against deepfake technology, these strategies are adhered to by us and should help firms safeguard their data and maintain client trust. If in-house expertise is insufficient or not practical due to economic reasons, collaborating with a cybersecurity specialist is strongly recommended.

Based on the latest information available, the most common cybersecurity threats faced by accounting firms in 2025 include:

Phishing and social engineering attacks

With these types of attacks, Cybercriminals use sophisticated techniques to trick employees into revealing sensitive information or downloading malware, nowadays even with AI assisted tools. Phishing remains one of the biggest threats to accounting firms. These attacks often involve:

• Emails from spoofed (“look-alike”) addresses that appear legitimate
• Urgent requests designed to override normal procedures
• SMS-based “smishing” attacks
• AI-generated phishing emails that mimic trusted sources
• Fake websites mimicking official portals

How to mitigate or avoid phishing attack?

• Employee training: Regularly train employees to recognize phishing attempts and suspicious messages. You can even run internal drills to measure response and report rates. We’re not going to reveal whether we’ve done this ourselves 😊
• Email filtering: Most email platforms such as the ones provided by Microsoft of Google have in-built spam and “suspicious” email filtering. However, you can implement advanced email filtering solutions to detect and block phishing emails. This is especially useful if you tailor your defence to your industry-typical attempts and use previous attempts as a learning to adjust settings.
• Multi-Factor Authentication (MFA): MFA typically means using your phone after you’ve entered your password to provide an additional passcode. MFA quickly became a standard for virtually all systems handling sensitive data. It is a minor inconvenience to users compared to the massive risk mitigation it provides. We use MFA extensively, and strongly recommend to anyone to require MFA for access to sensitive systems to prevent unauthorized access.
• Incident Response Plan: Although a basic ISMS requirement, an organization is way better off if it has a plan to handle a security incident should one occur. Develop a clear response plan in case of a successful phishing attempt by having a playbook for quickly mass-resetting passwords or locking out particular users.

Ransomware

Ransomware continues to be a serious threat, capable of encrypting files and halting operations until a ransom is paid. This type of threat became famous in the late 2010s, with the most successful ransomware attacks making it to international news.

How to mitigate or avoid ransomware attacks:

• Regular data backups: Ensure that critical data is backed up frequently and stored offline. At scale this may require serious resources – imagine daily backups on terabytes of data like we do at Process Solutions.
• Endpoint protection: An Endpoint is typically your employee’s computers. Deploy robust antivirus and endpoint detection response (EDR) solutions. There are many solutions like this in the market such as Microsoft Defender or ESET Endpoint Security.
• Software updates: If you’ve ever wanted to quickly log out to leave work, but Windows Update required you to stay a few extra minutes to just do its thing, this is part of the reason why it’s important. Regularly update operating systems and software to patch vulnerabilities.
• Email security: Block attachments from unknown senders and scan all email attachments. This is part of our employee training package, and most email providers also offer some level of protection, but ultimately, we have to let users open attachments – we just need to make sure they are acting as responsibly as possible before doing so!
• Network segmentation: In your everyday usage you should not notice working with applications that are distributed on several networks, but one of the most important actions we can recommend is compartmentalizing your internal network. At PS, we have for example among others, our intranet, file server, accounting and payroll applications on separate networks. This makes development and IT support a bit trickier, but it’s worth it. Separate sensitive data from general networks to minimize the impact of an attack.

As you can see, Phishing and ransomware attacks can get you in serious trouble, and mitigating the risk of a successful attack is not trivial. One should be prepared and expect nothing less of its vendors handling sensitive data.

In our next article, we will continue to explore the most common cybersecurity threats faced by accounting firms in 2025, such as insider threats and the implications of remote work environments.