The Attachments section allows you to set up the security settings that will protect the team from malicious third parties trying to use malware, phishing, or spoofing. By default, Enable all settings is active, which will apply all the rules with the default settings:

• Disable all settings. Choosing this will turn off attachment security. This is not recommended, even if you have an external attachment security service.
• Customize settings. It is recommended to use this option instead of Enable all settings since, with this option, you can Choose an action to have control of what will happen to messages that are targeted by this rule. By default, Gmail will just show a warning regarding suspicious messages, but you can also choose to Move email to spam so that it can be checked manually if necessary:

Attachments that are suspected of containing malware will be kept in the inbox and simply show a warning by default. I recommend changing this to Move email to spam instead so that an administrator can choose whether the email should be deleted or allowed to be seen by the intended recipient.