Attackers are always trying to find new ways to infect computers by luring not only potential victims but also security controls like anti-virus products. Do you know what SYLK files are? SYmbolic LinK files (they use the .slk extension) are Microsoft files used to exchange data between applications, specifically spreadsheets[1]. In Windows environments, there are represented with an icon similar to Excel:
Article Link: https://isc.sans.edu/diary/rss/23687