My agents and customers see red “harmful programs” screens or “malicious” file warnings when trying to access Zendesk or downloading attachments.
Google Safe Browsing flagged one of your subdomain's attachments or webpages as harmful, malicious or unsafe. When this occurs on your Zendesk subdomain, it can cause all attachments or pages to be blocked by the browser, and presents a red screen error, until a successful review within Google Webmaster tools confirms that malware attachments were removed, or the page was remedied.
Google notifies Zendesk when they detect unsafe pages or attachments. Then, Zendesk removes the attachment and requests a review from Google to get any malware warnings cleared for the affected subdomain. If you see this page, contact the Zendesk support team for further help.
While Zendesk constantly monitors all accounts for errors and alerts, you are also able to do it yourself by following the instructions in Can I verify my subdomain to be used in Google Search Console?.
For more information about best practices on attachments and security see the articles below.