[2:8-16] Wolves in Sheep's Clothing

[2:8] and from [among] the people [there are some] who say:
'we believe in God and in the Era of Afterlife' and [then] they do not believe
[2:9] [do] they deceive God and those who believe [?]
and they don't deceive [anyone] except themselves and they don't realise it.
[2:10] in their hearts is a sickness
so God increases their sickness
and for them is a painful punishment for what they denied.
[2:11] and when it is said to them: 'do not [create] corruption in the Earth'
they say: 'indeed we are the righteous'
[2:12] o no - indeed it is they who are the corruptors but they don't realise.
[2:13] and when it is said to them: 'believe as the people believed'
they say: 'are we to believe as the fools believed?'
o no - indeed it is they  who are the fools but they don't know.
[2:14] and when they meet those who believe they say:
'we believe'
but when [the believers have passed and] they are alone with their adversaries (satans) they say:
'Indeed we are with you.  Indeed we are mocking [them]'
[2:15] God is mocking them and extends them in their blind transgression.
[2:16] They are those who bought misguidance for guidance
so their transaction didn't profit them and they were not guided.

The above verses describe a 3rd category of people: the "Hypocrites" (The false-believers, the undercover enemies,"Rejecters" disguised as "Believers".   The wolves in sheep's clothing). 

They may look like the most religious scholar, an imaam, a rabbi, a priest, a politician, an actor, etc. 

They warp the truth and corrupt the faith from within.  They receive a greater punishment and are in the lowest grade of Hell [4:145]

God speaks at more lengths about them (indicating there are more "hypocrite" wolves in sheep's clothing than the plain "rejecter" wolves). 
The hypocrites:

• for them is a painful punishment [2:10]
• they don't realise that they are deceiving none but themselves [2:9]
• they don't know that they are the "fools" [2:13]
• God is mocking them [2:15]
• God extends their blindness (misguidance) [2:15]

Their actions are:

• they are deceptive (trying to deceive and mock God and the believers) [2:9] [2:14]
• they say they believe in God and the Afterlife [2:8]
• they are two-faced (saying to the believers that they believe but behind their back they mock them) [2:14]
• they backbite (talk about people behind their back) [2:14]
• they converse and jest with the adversary [2:14]
• they call themselves the righteous [2:11]
• they call other people 'fools' (and evil names) [2:13]
• they don't realise that they are the "corruptors" [2:12]
• they are "transgressors" [2:15]

Their beliefs are:

• they do not believe [2:8]
• they deny [the truth, God, etc] (like the rejecters) [2:10]
• they are misguided [2:16]
• they are aware of the guidance [2:16]

The reason they do this is also explained:

• In their hearts is a sickness which increases [2:10]