While coming home recently, I noticed a delay on RER Line B due to “actes de malveillance," which means vandalism. It turns out that this was more than just run-of-the-mill vandalism; the SNCF (the national railway company) considers it organized sabotage. Somebody is trying to cause trouble for rail transport.
In addition to many minor incidents over the past few months, there have been major ones. In one recent case, the bad guys carefully cut a hole in a fence on a bridge passing over a high-speed TGV train line (the high speed lines have no grade crossings, only bridges and underpasses), then lowered themselves down and attached a length of steel reinforcement bar (the kind used to make reinforced concrete) on the 25,000-volt catenary above the tracks. When a train came by and hit the bar, the power was interrupted for an entire section of the line, and many TGV trains were stalled for hours. Fortunately, the train that actually hit the rebar was a special train that runs early every morning before the passenger trains to inspect the lines. The train was undamaged, as far as I know, but the catenary had to be repaired and the power restored.
The work was done by people who knew what they were doing and knew exactly when and how to best interfere with the operation of the line. This tends to imply an inside job, or a job by someone who knows the railways well and has some sort of grudge against them. No suspects have been found thus far.