A study on IP addresses  by scientists from TU Delft in the Netherlands and the Max-Planck-Institut at Saarland University in Germany proves IP data retention threatens citizens’ privacy: IP addresses can be unique and persistent tracking identifiers.
According to the study many devices can be tracked over time and across different networks. If only one of these devices is in your home network, all other devices can be tracked too, even if they use privacy safeguards.
The study estimates that about 19% of all households are affected without being aware of the problem. The majority of the affected devices are inexpensive Internet of things devices, thus the study underscores that blanket data retention especially affects average citizens who use inexpensive devices and make no additional effort to protect their communications.Digital freedom fighter and Member of the European Parliament Patrick Breyer (Pirate Party, Group Greens/European Free Alliance) explains:
“Citizens’ IP data is comparable to footprints and fingerprints on the Internet. A general and indiscriminate retention of our identity on the Internet allows for creating comprehensive personality and movement profiles of practically every citizen. Criminals know how to escape data retention. But ordinary citizens are caught up in general mass surveillance. Unfortunately, a great political consensus seems to exist on mandating indiscriminate IP data retention. Under no circumstances should all internet users be placed under general suspicion and online anonymity be abolished! There is no evidence that IP data retention significantly increases the crime clearance rate. In the absence of mandatory IP data retention Germany today has a higher cybercrime clearance rate than with IP data retention in place in 2009.”
 Said Jawad Saidi, Oliver Gasser, and Georgios Smaragdakis. 2022. One Bad Apple Can Spoil Your IPv6 Privacy. In ACM SIGCOMM Computer Communication Review, Volume 52, Issue 2, April 2022. ACM, New York, NY, USA, 9 pages.
 Council doc. WK 7294/2021 INIT, LIMITE, 10 June 2021
Diplomatic Correspondence of the German Foreign Office of 23 December 2021
– German only –