【資料】
◆QUARTERLY THREAT REPORT Q1 2019 (Proofpoint, 2019/05/28)
https://www.proofpoint.com/sites/default/files/pfpt-us-tr-q119-quarterly-threat-report-0528.pdf
【関連まとめ記事】
◆Proofpoint Q1 2019 Threat Report (まとめ)
https://malware-log.hatenablog.com/entry/Proofpoint_Report