insmod: ERROR: could not insert module simpleModule.ko: Operation not permitted

Question

I'm a beginner learning about linux kernel. I tried to insert a simple module but encountered the following error.

sudo insmod simpleModule.ko
[sudo] password: 
insmod: ERROR: could not insert module simpleModule.ko: Operation not permitted

Contents of my simpleModule.c file:

#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>

int simple_init(void) {
    printk(KERN_INFO "Loading module\n");
    return 0;
}

void simple_exit(void) {
    printk(KERN_INFO "Removing module\n");  
}

module_init(simple_init);
module_exit(simple_exit);

MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("Simple Module");

My Makefile:

obj-m +=simpleModule.o

all:
        make -C /lib/modules/$(shell uname -r)/build M=$(PWD) modules

clean:
        make -C /lib/modules/$(shell uname -r)/build M=$(PWD) clean

I'm using Ubuntu 20.04

Please help me in understanding this error and how to resolve it.