Backbiting:

There are those from them that show sorrow; so he will say: ‘so and  so is weak/pitied, it has caused me sorrow for what has happened to him and what the outcome was for him.’ So he who hears him thinks that he  has sorrow for him and that he is regretful and that his heart is covered in the attainment of recovery for him; and if it were possible  then he would add to that which was with him. He may also mention him in front of his enemies so that they may profit from it. So this; and  other than it is from amongst the greatest of the sicknesses of the heart as well as deceitfulness to Allah and His creation.

Source: Majmoo’ al-fataawaa Shaikh ul Islaam Ibn Taymiyyah vol 28 pages 236-238