The al-Qaeda plots were found inside encoded inside a movie stored in a digital disk, after police arrested 22-year-old Austrian Maqsood Lodin in Berlin last year.
He had returned from Pakistan via Budapest, Hungary, and then travelled overland to Germany, CNN reported.
The interrogators found the digital storage device and memory cards hidden in his underpants.
Inside them was a pornographic video called "Kick Ass" and a file marked "Sexy Tanja", the tv channel reported.
After several weeks of laborious efforts to crack a password and software to make the file almost invisible, German investigators discovered encoded inside the actual video a treasure trove of intelligence -- more than 100 al-Qaeda documents that included an inside track on some of the terror group's most audacious plots and a road map for future operations.
Claiming that the documents uncovered are "pure gold", US intelligence sources told CNN that they are the most important haul of al-Qaeda materials in the last year, besides those found when US Navy SEALs raided Osama bin Laden's compound in Abbottabad, Pakistan, a year ago and killed the al-Qaeda leader.
More From This Section
The future plots included the idea of seizing cruise ships and carrying out attacks in Europe similar to the gun attacks by Pakistani terrorists in Mumbai in November 2008.
In the fall of 2010, a year after the document was written, European intelligence agencies were scrambling to investigate a Mumbai-style plot involving German and other European militants, which sparked an unprecedented US State Department travel warning for Americans in Europe. PTI SSB AKJ AKD
SSB