A 25-year-old techie working with Infosys was strangled with a computer cable at her office in Pune on Sunday. A security guard of the building was arrested this morning in Mumbai. The motive is not known yet. K Rasila Raju, a software engineer from Kerala, was found near her desk at her workstation on the ninth floor of the Infosys office in the Rajiv Gandhi Infotech Park in Hinjewadi last night.