A cyberattack has spread across the United States and into parts of Western Europe, causing an internet outage that affected several popular websites Friday. Sites affected included the social network Twitter, money transfer services PayPal, music-streamer Spotify and the discussion site Reddit. WATCH: White House spokesman Josh Earnest on what they know A company that manages crucial parts of the internet’s infrastructure said it was under attack Friday morning. Dyn, whose servers reroute internet traffic by hosting the Domain Name System, or DNS, said it had resolved the first attack, only to face a second one later in the day. After fending off the second attack, Dyn, which is based in New Hampshire, said it was again experiencing problems in the evening. The U.S. Department of Homeland Security said it is investigating “all possible causes” of the outage. White House spokesman Josh Earnest called the attack malicious but said he had no information about who could be behind it. Internet users affected by the outage experienced sluggish surfing. The attack, called a distributed denial of service (DDOS) attack, occurs when hackers flood particular servers with internet traffic until they cannot handle the load and shut down. The attack also affected Airbnb, Netflix, Etsy, SoundCloud and The New York Times. According to Dyn, the issues started at 11:10 UTC Friday.