I've checked the creative: 67634662101 using an internal tool and found that it is detected as suspicious malware, due to the associated landing page which is calling a Malware URL directly through the third party server. Here’s the list of Bad URLs which are suspected to be the reason for it being highlighted as malware.
I’d suggest that you reach out to the third-party or advertiser to remove/change Bad URLs. Once this change is applied, DFP’s automated system will re-scan the creatives and a “safe to re-enable” notification will be sent if the issue is resolved.
This Help Center article highlights how DFP deals with malvertising. Hope this helps, please let me know if you have any questions, I'll be happy to assist you.