Estonia cyberattacks (2007)
After Estonia relocated a Soviet war memorial, distributed denial-of-service attacks took down government, banking, media and police websites for days. Estonia blamed Russia, and a Russian student was later convicted over the attacks.
Online banking and state services were disrupted for days, and Estonia pressed its NATO and EU allies for a coordinated response.
NATO opened a cyber defense center in Tallinn, and the episode became the reference case for attacks on a state's digital services.
It is the clearest precedent for a government pulling core online services offline under attack, and for how quickly availability attacks become a national security matter.
