Rangers boss Harry Redknapp has wasted no time in his quest to bolster his defensive resources by signing South Korea international Yun from Chunnam Dragons on a three-and-a-half year deal.
The left-back has been granted a work permit but will need to wait on visa clearance before he is eligible to play for the R's.
Yun joins fellow January arrivals Loic Remy and Tal Ben Haim at Loftus Road, where he will link up with compatriot Park Ji-sung.
Rangers - who lost Ryan Nelsen to the MLS after the 0-0 draw with Manchester City - have also made a formal bid for former Blackburn Rovers defender Samba, who is currently playing for Anzhi Makhachkala in Russia.
The offer is understood to have activated a release clause in Samba's contract; Samba moved to Anzhi in a four-year deal 12 months ago.
The news did not impress Anzhi manager Guus Hiddink who is with his squad at a training camp in Spain.
"I'm really upset with this situation as Samba departed even without saying goodbye to anyone of us," he said. "Whatever is going on, I believe, you should never ignore people with whom you were working side by side."
Meanwhile, QPR goalkeeper Aaron Lennox has agreed a new deal keeping him at Loftus Road until 2015.
The 19-year-old joined the Hoops from the Australian Institute of Sport in August 2011 and has signed a new two-year extension.
To find out more about live football on Sky sports, Click here