Facebook said police in Greece made two arrests last week in connection with a little-known spamming botnet called "Lecpetex," which used hacked computers to mine the Litecoin virtual currency. As many as 50,000 Facebook accounts were affected, and as many as 250,000 computers worldwide, primarily in Greece, Poland, Norway, India, Portugal, and the United States, according to a blog post on Tuesday from Facebook's Threat Infrastructure team.