Hi Daan,

If you’re an Office 365 customer whose mailboxes are hosted in Microsoft Exchange Online, your email messages are automatically protected against spam and malware. Office 365 has built-in malware and spam filtering capabilities that help protect inbound and outbound messages from malicious software and help protect you from spam.
Office 365 comes up with different security features like below ones.

1. Advanced Threat Protection helps by stopping these malicious links and attachments before they get to your inbox.  It opens the attachments and links in a virtual environment (complete separate from your environment) and checks for malicious activity before the email gets to your inbox.

2. Encrypted email basically ensures no one other than the intended recipient can open and read emails you send.

3. Azure Identity Protection uses machine learning to understand how you work and flags unusual activity. For example, it will learn where and when you typically log in, so if you log in from an unusual place and time, it can flag that. It’ll also detect multiple log ins in a short amount of time from multiple locations.

However, if you still feel the need for another antivirus for Office 365, there are a myriad of options you can choose from to suit your needs.

1. Bitdefender is the leading antivirus for Office 365, which protects against any sophisticated threats. You’ll find it easy to install and monitor remotely from a single, powerful cloud console, plus it is also very cost effective.

2. BullGuard antivirus for Office 365 incorporates innovative multi-layered defenses that block all forms of malicious threats, ensuring optimal performance. It is simple to navigate with an effective, user friendly design and easy to use dashboard interface with clearly marked features and actions.

3. Security Reviver will scan your PC and identify security threats and vulnerabilities. Security Reviver can quickly and safely remove these threats and prevent them from reoccurring.  Security Reviver is continuously updated to ensure you’re protected against the latest threats and vulnerabilities.
You can schedule Security Reviver to run at startup or any other time of day, ensuring you are in control of your protection. You can also choose a Quick, Deep or Custom scan depending on your needs and preferences.

I hope this helps.

Regards,
Lokesh