However you cannot rely on any package and must still take the other precautions listed here as new viruses appear all the time. When you run a program infected by a virus the virus is also activated and has an opportunity to damage data or spread. They are transferred from PC to PC on floppy disk, including floppy disks that do not have any files on them. Once a PC is infected the virus is likely to infect all floppy disks used in it. To avoid spreading boot sector viruses you should remember not to leave disks in your floppy drive when it is booted.
Macro viruses infect files, but files normally considered to be data files rather than software.
The macro may be designed to cause damage and to infect other documents, templates, or spreadsheets. Trojans are malicious computer programs which pretend to be some other benefical computer program, such as a game or useful utility. They rely on people being tricked into running them. When a trojan is run it may appear to do nothing, or do what it claims to, but at the same time it is secretly doing something else such as deleting your data files or compromising the security of your computer. The best protection against trojans is not to run executable programs from sources you don't trust.