Telefónica Europe business was rebranded to 'O2 Online' which continues in the UK as a mobile communications service provider tied to the O2 UK network. The Genie portal properties were rebranded O2 Active in UK, Germany, Ireland and the Netherlands, and Genie Asia became O2 Asia. O2 Asia became a subsidiary of O2 UK for governance purposes. On 31 October 2005, O2 agreed to be taken over by Telefónica, a Spanish telecommunications company, with a cash offer of £17.7 billion, or £2 per share. According to the merger announcement, O2 retained its name and continued to be based in the United Kingdom,
The O2 sound and security technology, including RFID smart card tagging of staff and VIP guests, and digitally managed sound. There are four computer server rooms to provide this technology. The complex is also covered by CCTV and security personnel. Arena visitors and their bags are screened with X-ray machines and metal detectors at the main entrance. The O2 Arena (referred to as the North Greenwich Arena for the 2012 Summer Olympics and Paralympics) is a 20,000 capacity venue, primarily used for live music. It is located at the centre of The O2 and is the first American-style, multi-purpose arena in London.