Vodafone Spain has accepted that 3,000 customers were potentially exposed to malware after Mariposa botnet agents strayed onto the HTC Magic smartphone.
The admission to Spanish media on Thursday follows a meeting between the mobile phone giant's Iberian arm and representatives from Panda Security.
The infection of microSD cards for the HTC Magic with the Mariposa information-stealing client and other strains of malware was first reported after Vodafone Spain supplied a malware-infected Android phone to a Panda worker earlier this month. Earlier this week a second infection was reported, involving a HTC Magic phone supplied by Vodafone to a security consultant at S21Sec.
The Panda worker at the centre of the outbreak told El Reg that Vodafone is replacing 3,000 HTC Magic smartphone microSD cards because it reckons they are infected, not as a precaution.
Vodafone, which has launched an investigation into the infection, maintains that the whole unfortunate business is "isolated and local". There's no evidence that HTC Magic smartphones supplied by the mobile phone giant elsewhere in Europe are affected.
However, new figures suggesting 3,000 users were exposed to the malware make it one of the biggest incidents of an IT supplier shipping pre-pwned mobile kit.
Initially it was thought that stray infection of a refurbished phone might be behind the Panda incident, but the sheer numbers now reportedly infected point to problems in Vodafone's quality assurance, or with a specific batch of smartphones. ®