A recent arrest in Texas revealed that Google checks email for child porn, using sophisticated image-comparing technology.

Now the arrest of an Eastern Pennsylvania man shows that Microsoft also does such screenings.

Actually, the tech giant has been actively involved for years, since developing software called PhotoDNA in 2009, according to Microsoft. Only files in transit -- being uploaded, emailed or downloaded -- are checked, a company source explained.

Tyler James Hoffman, 20, of Drums, Luzerne County, was taken into custody Thursday on child pornography charges because of a "cyber-tip" that originated with "Microsoft/Microsoft Skydrive," according to an affidavit of probable cause posted on the Smoking Gun website.

"According to Microsoft, this individual uploaded one (1) image" in April of a "pre-pubescent female" in a revealing pose with a sex toy, and the firm informed the National Center for Missing and Exploited Children, which got in touch with the Luzerne County District Attorney's Office, the affadavit continues.

Another image detected eight days later allegedly showed a girl about 10 to 13 years old having intercourse.

The Microsoft live.com email account associated with the images was linked to Hoffman's Facebook account, Facebook photos were matched to a driver's license photo, and after being found at his workplace on Thursday, Hoffman admitted to "trading and receiving images of child pornography on his mobile cellular device," according to the affidavit.

Hoffman was arraigned Friday and, unable to post the $50,000 bail, was taken to Monroe County Prison. A preliminary hearing was scheduled for Aug. 14 on four felony counts of disseminating child-sex images and one count of felony use of a communication device.

"Child pornography violates the law as well as our terms of service, which makes clear that we use automated technologies to detect abusive behavior that may harm our customers or others," according to Microsoft spokesman Mark Lamb.

Microsoft and Google don't store kiddie porn for comparison purposes, but rely on codes called "hashes" that were created from known images of abuse. In effect, Microsoft's PhotoDNA technology looks for signatures or red flags, like percentage of flesh tones.

Microsoft shared its PhotoDNA technology with the National Center for Missing & Exploited Children, leading to its use by other online service providers, including Facebook.

It's no secret that Google scans emails sent via its gmail service, since users are shown ads related to the content of emails. By law, companies are required to report discoveries of child pornography.

Contact staff writer Peter Mucha at 215-854-4342 or pmucha@phillynews.com.