Wikipedia was down in large parts of the UK as well as Poland, France, Germany and Italy during the weekend. This most popular information resource was hit with a Distributed Denial of Service (DDoS) attack - overwhelming domains or specific application infrastructures with massive traffic flows. The same fate met popular online role-playing game World of Warcraft Classic - the two attacks are most likely related. Operators behind a Twitter account “UkDrillas” claimed to be behind them, but this has not been confirmed.
To mitigate DDoS attacks it's advised to understand the points in company services where resources can be overloaded; ensure that company service providers are ready to deal with DDoS attacks and that company services can scale to deal with surges in concurrent sessions, as well as create an effective response, testing and monitoring plan.