TMitch Fileless malware: One day, bank employees discovered an empty ATM: no money, no sign of physical interaction with the machine, no malware. Since its experts Kaspersky Lab spent considerable time investigating this mysterious case, were able to not only understand the digital crime tools used in the robbery, but also reproduce the attack themselves, discovering a breach in the bank's security system. 
In February of 2017, Kaspersky Lab published the results of one research on mysterious fileless attacks on banks: criminals used malware that attacks memory to "infect" banking networks. But why do that?
The "ATMitch" case gave us the overall picture.
The investigation began after the bank's forensic experts recovered and shared with Kaspersky Lab two files that contained malware log files from the ATM hard drive (kl.txt and LogFile.txt). These were the only files left after the attack: the malicious executable files could not be recovered because the digital criminals had removed the malware after the robbery. But even this small amount of data was enough for Kaspersky Lab to conduct a successful research.
Erase / rewind
Within files recording, its experts Kaspersky Lab were able to identify snippets of information in plain text, a feature that helped them create a YARA rule for publicly storing malware and find a sample. YARA rules - basic search strings - help analysts find, group, and categorize related malware samples and link to them based on suspicious activity patterns in similar systems or networks.
After a day of waiting, the experts found a desired sample of malware - "tv.dll", or "ATMitch", as it was later named. This was found free twice: once in Kazakhstan and once in Russia.
This malicious software was installed and remote from an ATM through the target bank: remote management of ATM machines. After installing and connecting to the ATM, malware ATMitch communicates with the ATM as it is a legitimate software. This allows attackers to execute a list of commands, such as collecting information about the number of ATM cassettes. It also allows criminals to distribute money at any time, at the touch of a button.
Usually, criminals start by getting information about the amount of money a machine has. After that, a criminal may send a mandate to distribute any number of banknotes from any cassette. After withdrawing money in this odd way, criminals need only to grab money and leave. An ATM robbery like this takes only a few seconds!
Once the ATM robbery has taken place, the malware deletes its traces.
Who is behind the attacks?
It is not yet known who is behind the attacks. The use of open source exploits, common Windows utilities and unknown regions during its early stage of operation make it almost impossible to identify the group responsible. However, 'tv.dll', which usesin the ATM stage of the attack contains a Russian-speaking source, and known groups that could fit this profile are GCMAN and Carbanak.
“The attackers may still be active. But don't panic! Combating these types of attacks requires a specific skill set from the security professional who secured the target organization. Successfully hacking and exfiltrating data from a network can only be accomplished with common and legitimate tools. After the attack, the criminals can clear all the data which could lead to their detection without leaving any trace at all. To address these issues, forensics derived from memory is critical to analyzing malware and its operations. And as our case proves, a carefully directed incident response can help solve even the most 'perfect' digital crime," said Sergey Golovanov, Principal Security Researcher of Kaspersky Lab.
Technical details and compromise indicators are also provided to service customers Kaspersky Intelligence Services.
