LONDON — As the world began Friday to understand the dimensions of Wanna Decryptor 2.0, the ransomware that has crippled computers worldwide, a vacationing British cybersecurity researcher was already several steps ahead.

https://www.washingtonpost.com/news/worldviews/wp/2017/05/13/a-british-researcher-says-he-found-a-kill-switch-for-the-malware-crippling-computers-worldwide/?utm_term=.c2f5c3c8fb51