Thomson Reuters
US soldiers at a welcoming ceremony for US-led NATO troops near Orzysz, Poland, April 13, 2017.
Russia has been hacking the cellphones of NATO soldiers stationed near its border "to gain operational information, gauge troop strength and intimidate soldiers," according to The Wall Street Journal, which cited US and Western officials.
Moscow has denied the accusations, but Western officials told The Journal that the level of technology used indicates state-sponsored operations.
The incidents began in January at Estonia's Tapa military base when Estonian soldiers noticed their contacts were disappearing from their phones and music that they had never downloaded would start playing, The Journal reported.
Estonian troops on the base now have to follow a "no smartphones" policy and are forced to remove their SIM cards, according to The Journal, adding that they can only use the internet in certain secure areas.
It's gotten so bad that their superiors order them to jump into lakes during operations to make sure they're following the policy, and some soldiers are even wrapping their phones in condoms.
The victims of the phone hackings have largely been the 4,000 NATO troops currently stationed in Poland and other Baltic states, according to The Journal.
REUTERS/Zbigniew Janicki/Agencja Gazeta
US soldiers arrive in Zagan, Poland, as part of NATO deployment, January 12, 2017.
Perhaps the most notable victim was the commander of a NATO base in Poland, US Army Lt. Col. Christopher L'Heureux, who told The Journal that someone with a Russian IP address reported personal iPhone lost and was trying to get through its password protection.
"It had a little Apple map, and in the center of the map was Moscow," L'Heureux said. "It said, 'Somebody is trying to access your iPhone.'" He said he was also being physically tracked through the phone.
L'Heureux also said some of his soldiers have had their Facebook profiles hacked.
Supposed Russian agents have even been known to walk up to US troops in public areas in Latvia and Poland and start mentioning details about the soldiers' personal lives, according to The Journal.
US military and Western officials, however, have said these hacks are not much of a security risk - as NATO troops are trained to thwart such attacks - and are more harassing anything.
REUTERS/Ints Kalnins US Army soldiers leave a Black Hawk helicopter during the Suwalki gap 
"We have seen attempts to undermine troops deployed in this part of our Alliance, but our personnel are well-equipped to perform the mission at hand, despite hybrid challenges," NATO spokesman Lt. Cdr. Davide Galli told CNBC this week. "The kind of attacks are often complex and sophisticated, therefore it's not always possible to determine all factors in an unequivocal way."
This kind of psychological warfare has also been ongoing in Ukraine's Donbas for years between government forces and Russian-backed separatists.
Thomson Reuters Ukrainian armored vehicles seen during military exercises in the Donetsk region, September 28, 2017.
According to a December 2016 report, Russian hackers had been planting malware into a Ukrainian artillery Android app for the previous two years to track and target its units.
US intelligence experts later traced the malware back to Fancy Bear, a Russian hacking group believed to have been behind the hacking of the Democratic National Committee in 2016 and which has ties to Russia's military intelligence agency, the GRU.
Russian-backed separatists have also reportedly been known to send Ukrainian forces intimidating text messages.
A few months ago, one journalist and the Ukrainian troops with whom she was embedded all received a text message at the same time, saying "Ukrainian soldiers, they'll find your bodies when the snow melts."
Other text messages read, "Leave and you will live," or "Nobody needs your kids to become orphans."