Financial and government websites in Ukraine went down on Wednesday 23 February in a coordinated distributed denial of service attack.
The cyber assault came as Russian troops crossed into Ukraine and launched an ongoing attack on the country.
The invasion has also impacted wider Internet services in some Ukrainian cities.
On the 23rd, Donetsk suffered a multi-hour Internet disruption primarily affecting provider Eastnet, amid a wider power outage, potentially caused by targeted physical attacks on grid infrastructure.
That day, the Luhansk power plant came under attack, wiping out heat and power in Schastia and Vrubivka.
From Thursday morning, 24 February, Internet services have been severely disrupted in Kharkiv, Ukraine’s second-largest city. Particularly impacted are fixed-line services on provider Triolan. Update: Triolan has announced that it will temporarily be offering Internet services in the country for free.
About 25 miles from the Russian border, Kharkiv is one of a number of Ukrainian cities under attack.
On February 24, Kyiv Internet traffic has dropped 60 percent over the course of the day, Cloudflare CEO Matthew Prince said on Twitter.
The public-facing websites of the Cabinet of Ministers, Security Service of Ukraine, the Verkhovna Rada legislature, and the Ministry of Foreign Affairs were brought offline by DDoS attacks on the 23rd, according to Ukraine’s Center for Strategic Communications. The public website of Ukraine's largest financial institution, PrivatBank, was also taken down. English-language Kyiv Post said that it "has been under constant cyber attack today from the moment Russia launched its military offensive against Ukraine."
Disruptive data wiping malware has also been found on computers across Ukraine, as well as Latvia.
Update: On February 25, telco Mediana went offline 08:40 UTC (10:40am local). "Mediana is based in Melitopol in southeast Ukraine which was the site of a publicized explosion at the airport yesterday," Kentik director of Internet analysis Doug Madory said.
The attacks come after similar DDoS attacks on February 15, and a temporary disruption of Vodafone's mobile Internet connectivity in Luhansk, Eastern Ukraine on Thursday 17 February.
"Tonight, purposeful diversions were made on the lines of communication of the Vodafone operator in Luganskaya and Donetsk regions," Anton Gerashchenko, Adviser to the Minister of the Interior of Ukraine, said at the time, posting images of what appeared to be cut terrestrial fiber cables.
Update: As of February 24, Russian government websites also appear to be impacted by DDoS attacks.