"The topic of commensurability is important" in any imperative to gather information - that was the extent of German Chancellor Angela Merkel's criticism with regard to the Prism spying program during US President Barack Obama's visit to Berlin last week.

Merkel has reason to limit her criticism on the topic. Although the fact that large parts of Internet communication are being monitored was known necessarily known to the general public, the chancellor was unlikely to have been surprised.

German spies have also been sniffing around online - and on a large scale, not just in cases of concrete suspicion. The German Federal Intelligence Service (BND) is legally allowed to rifle through up to 20 percent of the communication between Germany and other countries, and monitor certain Internet search terms.

More money for the BND

The BND wants to expand its Internet monitoring program

But the BND lacks the capacity to actually exhaust its legally allowed monitoring. According to the German newsmagazine "Der Spiegel," the agency is currently only monitoring only about 5 percent of data traffic.

This is why the agency is planning to expand its server and computing capacity and add 100 staff people. The 100 million euros ($130 million) it says it needs for this, however, has not yet been allocated.

In 2011, the BND filtered out almost 330,000 separate telecommunications messages for closer inspection in the area of terrorism defense alone. For this, there's a list of 1,500 search terms, some combination of which must be mentioned in order to allow the filtering.

The information source for this is a report by a parliamentary control committee from March 2013. The committee, comprised of 11 parliamentarians, oversees all German intelligence. Apart from the BND, this includes the Constitutional Protection Office and the Military Counter-Intelligence Service.

Germans share info

Compared to the US National Security Agency (NSA) and the British Government Communications Headquarters (GCHQ), however, Germany's intelligence service is weak. German Intelligence Service expert Erich Schmidt-Eenboom said the scope of the personnel responsible for data make this clear.

The National Security Agency is based in the state of Maryland

"The NSA has 60,000 workers and also employs many external firms, while experts estimate that altogether 15,000 people work for the GCHQ," Schmidt-Eenboom said. He pointed out that, in contrast, the external electronic message department of the BND includes about 1,500 workers.

Since intelligence services of allied nations share information with each other - particularly in the field of terror defense - Germany also profits from the eavesdropping measures of the US and Great Britain.

This is especially the case with regard to German citizens, who are largely protected from the BND by a ban on gathering information within Germany. The German Constitutional Protection Office is responsible for any domestic spying, and even stricter national privacy regulations apply to it.

"Of course, it can't be ruled out that American intelligence services have gained information through means we are not aware of and wouldn't use in Germany," said Hartfried Wolff, a center-right parliamentarian and member of the control committee, in an interview with DW.

Millions of phone calls monitored

Hans-Georg Wieck, the former chief of the BND, said it's a good thing that intelligence services can share information: "How else is one supposed to take up the trail of terror attacks being planned domestically, when there's no tip from internal intelligence services?"

"Der Spiegel" reported that, each month, the NSA listens in on about half a billion separate communications in Germany - including telephone conversations, emails, text messages and chats. On an average day, the NSA listens to about 20 million phone conversations in Germany, according to internal NSA statistics cited by the magazine.

Friends spying on each other

Wolff is one of 11 German parliamentarians on the intelligence oversight committee

The fact that the governments of allied countries also spy on each other is another matter altogether. On Saturday (29.06.2013) it became known that American spying devices were hidden among EU representatives in Washington, D.C. The British daily "The Guardian" reported recently that the GCHQ in 2009 eavesdropped on friendly countries, even at an Internet café prepared for delegates.

"They did their job," said intel expert Schmidt-Eenboom, who was not surprised. "The agencies have to not only cover national security and serious crime, but also protect the economic interests of Great Britain," he said.

And even if the government was spying in the name of the fight against terror, the public wouldn't likely know - as secret intelligence services work secretly.