Adversaries may use binary padding to add junk data and change the on-disk representation of malware. This can be done without affecting the functionality or behavior of a binary, but can increase the size of the binary beyond what some security tools are capable of handling due to file size limitations. 

Binary padding effectively changes the checksum of the file and can also be used to avoid hash-based blocklists and static anti-virus signatures.(Citation: ESET OceanLotus) The padding used is commonly generated by a function to create junk data and then appended to the end or applied to sections of malware.(Citation: Securelist Malware Tricks April 2017) Increasing the file size may decrease the effectiveness of certain tools and detection capabilities that are not designed or configured to scan large files. This may also reduce the likelihood of being collected for analysis. Public file scanning services, such as VirusTotal, limits the maximum size of an uploaded file to be analyzed.(Citation: VirusTotal FAQ) 
Binary Padding
source_name: mitre-attack  url: https://attack.mitre.org/techniques/T1027/001  external_id: T1027.001     source_name: ESET OceanLotus  description: Foltýn, T. (2018, March 13). OceanLotus ships new backdoor using old tricks. Retrieved May 22, 2018.  url: https://www.welivesecurity.com/2018/03/13/oceanlotus-ships-new-backdoor/     source_name: Securelist Malware Tricks April 2017  description: Ishimaru, S.. (2017, April 13). Old Malware Tricks To Bypass Detection in the Age of Big Data. Retrieved May 30, 2019.  url: https://securelist.com/old-malware-tricks-to-bypass-detection-in-the-age-of-big-data/78010/     source_name: VirusTotal FAQ  description: VirusTotal. (n.d.). VirusTotal FAQ. Retrieved May 23, 2019.  url: https://www.virustotal.com/en/faq/     