Machine learning algorithms represent the intelligence that controls many information systems and applications around us. As such, they are targeted by attackers to impact their decisions. Text created by machine learning algorithms has many types of applications, some of which can be considered malicious especially if there is an intention to present machine-generated text as human-generated. In this paper, we surveyed major subjects in adversarial machine learning for text processing applications. Unlike adversarial machine learning in images, text problems and applications are heterogeneous. Thus, each problem can have its own challenges. We focused on some of the evolving research areas such as: malicious versus genuine text generation metrics, defense against adversarial attacks, and text generation models and algorithms. Our study showed that as applications of text generation will continue to grow in the near future, the type and nature of attacks on those applications and their machine learning algorithms will continue to grow as well. Literature survey indicated an increasing trend in using pre-trained models in machine learning. Word/sentence embedding models and transformers are examples of those pre-trained models. Adversarial models may utilize same or similar pre-trained models as well. In another trend related to text generation models, literature showed effort to develop universal text perturbations to be used in both black-and white-box attack settings. Literature showed also using conditional GANs to create latent representation for writing types. This usage will allow for a seamless lexical and grammatical transition between various writing styles. In text generation metrics, research trends showed developing successful automated or semi-automated assessment metrics that may include human judgement. Literature showed also research trends of designing and developing new memory models that increase performance and memory utilization efficiency without validating real-time constraints. Many research efforts evaluate different defense model approaches and algorithms. Researchers evaluated different types of targeted attacks, and methods to distinguish human versus machine generated text.

The growing use of media has led to the development of several machine learning (ML) and natural language processing (NLP) tools to process the unprecedented amount of social media content to make actionable decisions. However, these ML and NLP algorithms have been widely shown to be vulnerable to adversarial attacks. These vulnerabilities allow adversaries to launch a diversified set of adversarial attacks on these algorithms in different applications of social media text processing. In this article, we provide a comprehensive review of the main approaches for adversarial attacks and defenses in the context of social media applications with a particular focus on key challenges and future research directions. In detail, we cover literature on six key applications: 1) rumors detection; 2) satires detection; 3) clickbaits and spams identification; 4) hate speech detection; 5) misinformation detection; and 6) sentiment analysis. We then highlight the concurrent and anticipated future research questions and provide recommendations and directions for future work.

The capability of generating high-quality source code using large language models (LLMs) reduces software development time and costs. However, recent literature and our empirical investigation in this work show that while LLMs can generate functioning code, they inherently tend to introduce security vulnerabilities, limiting their potential. This problem is mainly due to their training on massive open-source corpora exhibiting insecure and inefficient programming practices. Therefore, automatic optimization of LLM prompts for generating secure and functioning code is a demanding need. This paper introduces PromSec, an algorithm for prompt optimization for secure and functioning code generation using LLMs. In PromSec, we combine 1) code vulnerability clearing using a generative adversarial graph neural network, dubbed as gGAN, to fix and reduce security vulnerabilities in generated codes and 2) code generation using an LLM into an interactive loop, such that the outcome of the gGAN drives the LLM with enhanced prompts to generate secure codes while preserving their functionality. Introducing a new contrastive learning approach in gGAN, we formulate the code-clearing and generation loop as a dual-objective optimization problem, enabling PromSec to notably reduce the number of LLM inferences. As a result, PromSec becomes a cost-effective and practical solution for generating secure and functioning codes. Extensive experiments conducted on Python and Java code datasets confirm that PromSec effectively enhances code security while upholding its intended functionality. Our experiments show that despite the comprehensive application of a state-of-the-art approach, it falls short in addressing all vulnerabilities within the code, whereas PromSec effectively resolves each of them. Moreover, PromSec achieves more than an order-of-magnitude reduction in operational time, number of LLM queries, and security analysis costs. Furthermore, prompts optimized with PromSec for a certain LLM are transferable to other LLMs across programming languages and generalizable to unseen vulnerabilities in training. This study presents an essential step towards improving the trustworthiness of LLMs for secure and functioning code generation, significantly enhancing their large-scale integration in real-world software code development practices.

Prediction of taxi service demand and supply is essential for improving customer experience and provider's profit. Recently, graph neural networks (GNNs), modeling city areas as nodes in a transportation graph, have been shown efficient for this application as they utilize both local node features and the graph structure in the prediction. Still, further improvement can be achieved by either simultaneously exploiting different types of nodes/edges in the graphs or enlarging the scale of the transportation graph. However, both alternatives are challenged by the scalability of GNNs. An immediate remedy to the scalability challenge is to decentralize the GNN operation. In return, as shown by our theoretical analysis and experimentation, this creates prohibitively excessive node-to-node communication. In this paper, we first propose a heterogeneous GNN-LSTM algorithm for improved taxi-level demand and supply forecasting utilizing several edge types in the graph. Then, to enable the large-scale application of this approach, we propose a semi-decentralized GNN inference approach that achieves scalability at minimized communication and computation overheads. This is achieved by utilizing multiple cloudlets; data centers with moderate computation and communication capabilities that can fit at cellular base stations. Extensive experiments over real data show the advantage of the proposed GNN-LSTM algorithm in improving prediction accuracy, and the ability of the proposed semi-decentralized GNN approach in reducing the overall inference time by about an order of magnitude compared to centralized and decentralized inference schemes.

Cognitive radio is an intelligent and adaptive radio that improves the utilization of the spectrum by its opportunistic sharing. However, it is inherently vulnerable to primary user emulation and jamming attacks that degrade the spectrum utilization. In this paper, an algorithm for the detection of primary user emulation and jamming attacks in cognitive radio is proposed. The proposed algorithm is based on the sparse coding of the compressed received signal over a channel-dependent dictionary. More specifically, the convergence patterns in sparse coding according to such a dictionary are used to distinguish between a spectrum hole, a legitimate primary user, and an emulator or a jammer. The process of decision-making is carried out as a machine learning-based classification operation. Extensive numerical experiments show the effectiveness of the proposed algorithm in detecting the aforementioned attacks with high success rates. This is validated in terms of the confusion matrix quality metric. Besides, the proposed algorithm is shown to be superior to energy detection-based machine learning techniques in terms of receiver operating characteristics curves and the areas under these curves.

The identification of spectrum opportunities is a pivotal requirement for efficient spectrum utilization in cognitive radio systems. Spectrum prediction offers a convenient means for revealing such opportunities based on the previously obtained occupancies. As spectrum occupancy states are correlated over time, spectrum prediction is often cast as a predictable time-series process using classical or deep learning-based models. However, this variety of methods exploits time-domain correlation and overlooks the existing correlation over frequency. In this paper, differently from previous works, we investigate a more realistic scenario by exploiting correlation over time and frequency through a 2D-long short-term memory (LSTM) model. Extensive experimental results show a performance improvement over conventional spectrum prediction methods in terms of accuracy and computational complexity. These observations are validated over the real-world spectrum measurements, assuming a frequency range between 832-862 MHz where most of the telecom operators in Turkey have private uplink bands.