Germany's Federal Criminal Police Office (BKA) warns that phone scams directed against the elderly are becoming more popular in the country.
One million Germans have been robbed of €117 million through telephone scams since 2008, the BKA reports.
Recently there has been a surge of 'grandchild ploys' targeting old people who live by themselves.
They will receive a phone call from a young person saying something along the lines of "Hey grandma, it's me!"
The scammers go on to convince their victim that they are a close relative in need of urgent help in the form of money.
Although this type of fraudulent phone call has been claiming victims for a long time, it is still very successful.
The BKA also warns of a wave of calls from people pretending to be police officers.
These 'officers' tell their victims of a spree of break-ins in their neighbourhood. They will sometimes spend hours talking about the situation and establishing trust with their prey, explains Joachim Ludwig of the Association of Criminal Police (BDK).
He says that the criminals' end-game is to convince their victims to "hide their valuables away from the house or give them to someone claiming to be a police officer for them to hide."
"These fraud cases are a matter of mass tort," says the BKA. A mass tort involves a large number of plaintiffs making the case against a few defendants for the same or a similar crime.
There aren't concrete numbers on the frequency of the different types of these crimes because various tricks such as the grandchild ploys and the fake police scams are lumped into one category of crime, and sometimes they are not reported at all.
But a recent case in North Rhine-Westphalia shows how huge this method of criminality can become.
Scammers in the western state had been regularly preying on the elderly with a creative but dastardly scheme.
They would convince their victims that they were calling from a reputable lottery organization, and that their prey had a high chance of winning more money if they first placed a sizeable bet.
The perpetrators never paid out the winnings, and they managed to fool at least 270,000 victims across the whole state, robbing them of over €66 million.
These sorts of phone scams can go very far. If the lottery scheme is successful, the fraudsters might then call the same person again, claiming to be the police or a lawyer.
They will explain that the payment to the betting pool was illegal, and in order to avoid a messy lawsuit or investigation, they need to pay another sum of money to this seemingly legitimate caller.
"Even when a victim has no more money and all their savings have been eaten up, the perpetrators will not leave them alone and will ask them to take out a loan or credit," explains the BKA.
Bianca Biwer of the German victim protection organization Weisser Ring explains how the criminals are so successful.
"Fraudsters tend to present themselves as representatives of a serious organization or authority, such as the BKA, the police or a public prosecutor," she says, highlighting that this puts victims under pressure and intimidates them.
Hermann-Josef Borjans, a police chief from Bonn, sees old people as especially vulnerable. He explains that they can't imagine themselves as being victims of crime and they like social contact or just want to help.
"It's important for the elderly to be wary," he warns. "When receiving unusual phone calls, they must ask themselves: 'can this be true?'"