How to make links in post nofollow?

[datoneer]

Hi!
Guys need to this to reduce spam!
Making all links in user post nofollow.
Anyone know how to do this?
Plz help!

[HMBeaty]

<a href="https://vborg.vbsupport.ru/showthread.php?t=228614" target="_blank">https://vborg.vbsupport.ru/showthread.php?t=228614</a>

[datoneer]

Not working. I don't understand this. Where's the problem, i tried in vb bbcode options too, but nothing. How to make this to be nofollow. vb version 4.1.5