Garbage code insertion is a cheap way of making code look complicated. A code is simply injected with a code or a sequence of code that actually does nothing. In the following code snippet, try to identify all of the garbage codes:

    mov eax, [esi]
    pushad
    popad
    xor eax, ffff0000h
    nop
    call loc_004017f
    shr eax, 4
    add ebx, 34h
    sub ebx, 34h
    push eax
    ror eax, 5
    and eax, 0ffffh
    pop eax
    jmp loc_0040180
loc_004017f:
    ret

Removing the garbage codes should reduce it down to this code:

    mov eax, [esi]
    xor eax, ffff0000h
    shr eax, 4
    jmp loc_0040180

A lot of malware employs this technique to quickly generate variants of its own code. It may increase the size of code, but as a result, it makes it undetectable by signature-based anti-malware software.